Semiconductor device having diode-built-in igbt and semiconductor device having diode-built-in dmos

ABSTRACT

A semiconductor device includes: a semiconductor substrate; a diode-built-in insulated-gate bipolar transistor having an insulated-gate bipolar transistor and a diode, which are disposed in the substrate, wherein the insulated-gate bipolar transistor includes a gate, and is driven with a driving signal input into the gate; and a feedback unit for detecting current passing through the diode. The driving signal is input from an external unit into the feedback unit. The feedback unit passes the driving signal to the gate of the insulated-gate bipolar transistor when the feedback unit detects no current through the diode, and the feedback unit stops passing the driving signal to the gate of the insulated-gate bipolar transistor when the feedback unit detects the current through the diode.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on Japanese Patent Applications No.2007-229959 filed on Sep. 5, 2007, No. 2007-268328 filed on Oct. 15,2007, No. 2008-96017 filed on Apr. 2, 2008 and No. 2008-96018 filed onApr. 2, 2008, the disclosures of which are incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to a semiconductor device having adiode-built-in IGBT, and a semiconductor device having a diode-built-inDMOS.

BACKGROUND OF THE INVENTION

In the past, a proposal has been made of an IGBT with a body diode thathas diode elements and IGBT elements formed in the same semiconductorsubstrate (refer to, for example, a patent document 1, that is,JP-A-6-351226 corresponding to U.S. Pat. No. 5,559,656). The IGBT with abody diode has the anode electrodes of the diode elements and theemitter electrodes of the IBGT elements formed in common with eachother, and has the cathode electrodes of the diode elements and thecollector electrodes of the IGBT elements formed in common with eachother. The IGBT with a body diode is incorporated in, for example, aninverter circuit, and used to control a load according to a pulse-widthmodulation (PWM) control method.

However, when the conventional IGBT with a body diode is incorporated inan inverter circuit, a gate signal for the IGBT elements is, inprinciple, a signal that has the phase thereof inverted between theupper and lower arms of the inverter circuit. The gate signal istherefore inputted to the IGBT elements even at the timing at which, forexample, the diode elements freewheel. In other words, the action of thediode elements and the action of the IGBT elements take placesimultaneously. Incidentally, the action of the IGBT elements signifiesthat the gate signal is inputted to the IGBT elements.

As mentioned above, when the action of the diode elements and the actionof the IGBT elements take place simultaneously, since the electrodes areformed in common, if the channels in the IGBT elements conduct, theanodes and cathodes of the diode elements are brought to the samepotential. Consequently, the body diode including the diode elementscannot readily act in a forward direction due to the gate potential ofthe IGBT elements. As a result, the forward voltage Vf of the diodeelements increases, and the forward loss caused by the diode elementsincreases.

As a method for avoiding the foregoing problem by devising a devicestructure, formation of a diode-only region, that is, a region devoid ofa gate separately from a body diode of an IGBT is conceivable asdescribed in, for example, “Proceedings of 2004 International Symposiumon Power Semiconductor Devices & Amp; ICs” (pp 261-264). However, aregion that does not act as the IGBT, that is, a region that performs adiode action alone expands. Consequently, if the diode-only region isformed with a chip size left unchanged, the on-state voltage of the IGBTincreases. Incidentally, if the on voltage of the diode is fixed, thechip size increases.

On the other hand, for dc-dc converters, a method of implementingsynchronous rectification control by incorporating a double-diffusedmetal-oxide FET semiconductor (DMOS) with a body diode as a switchingdevice in a control circuit is widely known. When a current flows intodiode elements included in the DMOS with a body diode, a forward voltageis developed in the diode elements and a dc loss equivalent to theforward voltage is produced. Therefore, when such synchronousrectification control is implemented, a method of sensing the current inDMOS elements using a current transformer for the purpose of bringing agate signal for reflux DMOS elements to an on-state voltage level isgenerally adopted (refer to, for example, JP-A-2004-180386).

However, the current transformer is needed as a current sensing device.This poses a problem in that the circuit scale gets larger. As a methodthat solves the problem, a method of monitoring a voltage across theterminals of a switching device is conceivable (refer to, for example,JP-A-2004-208407). However, according to this method, a control IC whoseinput terminal can withstand a high supply voltage is needed. Sincenoise resistivity is strictly requested at the time of conducting a highvoltage, addition of a protective device or any other highly resistivedesign is needed. This poses a problem in that the cost of the controlIC increases.

Thus, it is required to prevent an increase in a forward loss caused bya diode, which is included in a semiconductor device including an IGBTwith a body diode, by avoiding the interference of the action of diodeelements with the action of IGBT elements. Further, it is required toprevent an increase in a loss in a forward voltage of the diodeelements, which are included in a semiconductor device including a DMOSwith a body diode, by synchronizing the action of the diode elementswith the action of DMOS elements.

As described in, for example, JP-A-2004-88001, a method of using currentdetection elements, which have the same structure as insulated-gatebipolar transistor (IGBT) elements do, to detect whether a current hasflowed into freewheeling diode (FWD) elements, feeding back the resultof the detection to a gate drive circuit, and setting the gate drivingsignal for the IGBT elements to an off-state voltage level when the FWDelements are put into action is conceivable. However, since the currentdetection elements having such a structure are affected by a gatepotential, a current cannot readily flow into the current detectionelements. A detective voltage cannot therefore be developed at thecurrent detection elements. In other words, feedback cannot be preciselyperformed, and an increase in a forward loss caused by the commutationdiode elements cannot be effectively suppressed.

Thus, it is required to provide a semiconductor device capable ofsuppressing an increase in a forward loss caused by FWD elements despitea construction having the FWD elements incorporated in IGBT elements.

SUMMARY OF THE INVENTION

In view of the above-described problem, it is an object of the presentdisclosure to provide a semiconductor device having a diode-built-inIGBT. It is another object of the present disclosure to provide asemiconductor device having a diode-built-in DMOS.

According to a first aspect of the present disclosure, a semiconductordevice includes: a semiconductor substrate; a diode-built-ininsulated-gate bipolar transistor having an insulated-gate bipolartransistor and a diode, which are disposed in the substrate, wherein theinsulated-gate bipolar transistor includes a gate, and is driven with adriving signal input into the gate; and a feedback unit for detectingcurrent passing through the diode. The driving signal is input from anexternal unit into the feedback unit. The feedback unit passes thedriving signal to the gate of the insulated-gate bipolar transistor whenthe feedback unit detects no current through the diode. The feedbackunit stops passing the driving signal to the gate of the insulated-gatebipolar transistor when the feedback unit detects the current throughthe diode.

In the above semiconductor device the interference of the action of thediode with the action of the IGBT can be avoided. Further, since thediode and IGBT are simultaneously turned on, an increase in a loss inthe forward voltage of the diode can be prevented.

According to a second aspect of the present disclosure, a semiconductordevice includes: a semiconductor substrate; a diode-built-in doublediffused metal oxide semiconductor transistor having a double diffusedmetal oxide semiconductor transistor and a diode, which are disposed inthe substrate; wherein the double diffused metal oxide semiconductortransistor includes a gate, which is driven with a driving signal inputinto the gate; and a feedback unit for detecting current passing throughthe diode. The driving signal is input from an external unit into thefeedback unit. The feedback unit stops driving the double diffused metaloxide semiconductor transistor when the feedback unit detects no currentthrough the diode, and the feedback unit drives the double diffusedmetal oxide semiconductor transistor so that current having a directionequal to a forward direction of the forward current flows through thedouble diffused metal oxide semiconductor transistor when the feedbackunit detects a forward current through the diode.

In the above device, an increase in a dc loss equivalent to a forwardvoltage occurring when the forward current flows into the diode can beprevented.

According to a third aspect of the present disclosure, a semiconductordevice includes: a semiconductor substrate; a diode-built-ininsulated-gate bipolar transistor having an insulated-gate bipolartransistor and a diode unit, which are disposed in the substrate,wherein the insulated-gate bipolar transistor includes a gate, and isdriven with a driving signal input into the gate, wherein the diode unitincludes a diode element and a diode current sensing element, andwherein the diode current sensing element passes current in proportionto current flowing through the diode element; a sensing resistor coupledwith the diode current sensing element; and a feedback unit. The drivingsignal is input from an external unit into the feedback unit. Thefeedback unit provides a first diode current threshold, which defineswhether the diode element passes current. The feedback unit compares avoltage between two ends of the sensing resistor with the first diodecurrent threshold. The feedback unit passes the driving signal to thegate of the insulated-gate bipolar transistor so that the insulated-gatebipolar transistor turns on when the voltage between two ends of thesensing resistor is equal to or larger than the first diode currentthreshold, and the feedback unit stops passing the driving signal to thegate of the insulated-gate bipolar transistor so that the insulated-gatebipolar transistor turns off when the voltage between two ends of thesensing resistor is smaller than the first diode current threshold.

In the above device, the interference between the action of the diodeand the action of the IGBT can be avoided. Further, an increase in aloss in the forward voltage of the diode can be prevented.

According to a fourth aspect of the present disclosure, a semiconductordevice includes: a semiconductor substrate; a diode-built-ininsulated-gate bipolar transistor having an insulated-gate bipolartransistor and a diode unit, which are disposed in the substrate,wherein the insulated-gate bipolar transistor includes a gate, and isdriven with a driving signal input into the gate, wherein the diode unitincludes a diode element and a diode current sensing element, andwherein the diode current sensing element passes current in proportionto current flowing through the diode element; a sensing resistor coupledwith the diode current sensing element; and first and second feedbackunits. The first feedback unit provides a decision threshold, whichdefines whether the insulated-gate bipolar transistor is in an on-state.The first feedback unit compares a gate voltage of the insulated-gatebipolar transistor with the decision threshold. The first feedback unitoutputs a first diode current threshold when the gate voltage is largerthan the decision threshold. The first diode current threshold showsthat the insulated-gate bipolar transistor is in the on-state. The firstfeedback unit outputs a second diode current threshold when the gatevoltage is equal to or smaller than the decision threshold. The seconddiode current threshold shows that the insulated-gate bipolar transistoris in an off-state, and the second diode current threshold is largerthan the first diode current threshold. The driving signal is input froman external unit into the second feedback unit. The second feedback unitcompares a voltage between two ends of the sensing resistor with thefirst diode current threshold when the voltage between two ends of thesensing resistor decreases. The feedback unit passes the driving signalto the gate of the insulated-gate bipolar transistor so that theinsulated-gate bipolar transistor turns on when the voltage between twoends of the sensing resistor is equal to or larger than the first diodecurrent threshold in a case where the voltage between two ends of thesensing resistor decreases. The feedback unit stops passing the drivingsignal to the gate of the insulated-gate bipolar transistor so that theinsulated-gate bipolar transistor turns off when the voltage between twoends of the sensing resistor is smaller than the first diode currentthreshold in a case where the voltage between two ends of the sensingresistor decreases. The second feedback unit compares the voltagebetween two ends of the sensing resistor with the second diode currentthreshold when the voltage between two ends of the sensing resistorincreases. The feedback unit stops passing the driving signal to thegate of the insulated-gate bipolar transistor so that the insulated-gatebipolar transistor turns off when the voltage between two ends of thesensing resistor is smaller than the second diode current threshold in acase where the voltage between two ends of the sensing resistorincreases, and the feedback unit passes the driving signal to the gateof the insulated-gate bipolar transistor so that the insulated-gatebipolar transistor turns on when the voltage between two ends of thesensing resistor is equal to or larger than the second diode currentthreshold in a case where the voltage between two ends of the sensingresistor increases.

In the above device, the IGBT can be controlled stably without beingvibrated. Moreover, the interference between the action of the diode andthe action of the IGBT can be avoided in order to prevent an increase ina forward loss in the diode.

According to a fifth aspect of the present disclosure, a semiconductordevice includes: a semiconductor substrate; a diode-built-ininsulated-gate bipolar transistor having an insulated-gate bipolartransistor unit and a diode unit, which are disposed in the substrate,wherein the insulated-gate bipolar transistor unit includes aninsulated-gate bipolar transistor and an IGBT current sensing element,wherein the insulated-gate bipolar transistor includes a gate, and isdriven with a driving signal input into the gate, wherein the IGBTcurrent sensing element passes current in proportion to current flowingthrough the insulated-gate bipolar transistor, wherein the diode unitincludes a diode element and a diode current sensing element, andwherein the diode current sensing element passes current in proportionto current flowing through the diode element; a sensing resistor coupledwith the IGBT current sensing element and the diode current sensingelement; an IGBT feedback unit; and a diode Schmitt unit. The drivingsignal is input from an external unit into the IGBT feedback unit. TheIGBT feedback unit provides an over current threshold, which defineswhether over current passes through the insulated-gate bipolartransistor. The IGBT feedback unit compares a voltage between two endsof the sensing resistor with the over current threshold. The IGBTfeedback unit passes the driving signal to the gate of theinsulated-gate bipolar transistor so that the insulated-gate bipolartransistor turns on when the voltage between two ends of the sensingresistor is equal to or smaller than the over current threshold. TheIGBT feedback unit stops passing the driving signal to the gate of theinsulated-gate bipolar transistor so that the insulated-gate bipolartransistor turns off when the voltage between two ends of the sensingresistor is larger than the first diode current threshold. The drivingsignal is further input from the external unit into the diode Schmittunit. The diode Schmitt unit provides a first diode current threshold,which defines whether the diode element passes current, and a seconddiode current threshold, which is larger than the first diode currentthreshold. The diode Schmitt unit compares the voltage between two endsof the sensing resistor with the first diode current threshold when thevoltage between two ends of the sensing resistor decreases. The diodeSchmitt unit passes the driving signal to the gate of the insulated-gatebipolar transistor so that the insulated-gate bipolar transistor turnson when the voltage between two ends of the sensing resistor is equal toor larger than the first diode current threshold in a case where thevoltage between two ends of the sensing resistor decreases. The diodeSchmitt unit stops passing the driving signal to the gate of theinsulated-gate bipolar transistor so that the insulated-gate bipolartransistor turns off when the voltage between two ends of the sensingresistor is smaller than the first diode current threshold in a casewhere the voltage between two ends of the sensing resistor decreases.The diode Schmitt unit compares the voltage between two ends of thesensing resistor with the second diode current threshold when thevoltage between two ends of the sensing resistor increases. The diodeSchmitt unit stops passing the driving signal to the gate of theinsulated-gate bipolar transistor so that the insulated-gate bipolartransistor turns off when the voltage between two ends of the sensingresistor is smaller than the second diode current threshold in a casewhere the voltage between two ends of the sensing resistor increases,and the diode Schmitt unit passes the driving signal to the gate of theinsulated-gate bipolar transistor so that the insulated-gate bipolartransistor turns on when the voltage between two ends of the sensingresistor is equal to or larger than the second diode current thresholdin a case where the voltage between two ends of the sensing resistorincreases.

In the above device, the diode Schmitt unit can prevent a chatteringfrom occurring during implementation of feedback control in the IGBT.Moreover, when an over current has flowed into the IGBT, the IGBTfeedback unit ceases driving the IGBT so as to protect the IGBT frombeing broken.

According to a sixth aspect of the present disclosure, a semiconductordevice includes: a semiconductor substrate; a diode-built-ininsulated-gate bipolar transistor having an insulated-gate bipolartransistor unit and a diode unit, which are disposed in the substrate,wherein the insulated-gate bipolar transistor unit includes aninsulated-gate bipolar transistor and an IGBT current sensing element,wherein the insulated-gate bipolar transistor includes a gate, and isdriven with a driving signal input into the gate, wherein the IGBTcurrent sensing element passes current in proportion to current flowingthrough the insulated-gate bipolar transistor, wherein the diode unitincludes a diode element and a diode current sensing element, andwherein the diode current sensing element passes current in proportionto current flowing through the diode element; a first sensing resistorcoupled with the IGBT current sensing element; a second sensing resistorcoupled with the diode current sensing element; an IGBT Schmitt unit;and a diode Schmitt unit. The driving signal is input from an externalunit into the IGBT Schmitt unit. The IGBT Schmitt unit provides a firstover current threshold, which defines whether over current passesthrough the insulated-gate bipolar transistor, and a second over currentthreshold, which is smaller than the first over current threshold.

The IGBT Schmitt unit compares a first voltage between two ends of thefirst sensing resistor with the first over current threshold when thefirst voltage increases. The IGBT Schmitt unit passes the driving signalto the gate of the insulated-gate bipolar transistor so that theinsulated-gate bipolar transistor turns on when the first voltage isequal to or smaller than the first over current threshold in a casewhere the first voltage increases. The IGBT Schmitt unit stops passingthe driving signal to the gate of the insulated-gate bipolar transistorso that the insulated-gate bipolar transistor turns off when the firstvoltage is larger than the first over current threshold in a case wherethe first voltage increases. The IGBT Schmitt unit compares the firstvoltage with the second over current threshold when the first voltagedecreases. The IGBT Schmitt unit stops passing the driving signal to thegate of the insulated-gate bipolar transistor so that the insulated-gatebipolar transistor turns off when the first voltage is larger than thesecond over current threshold in a case where the first voltagedecreases. The IGBT Schmitt unit passes the driving signal to the gateof the insulated-gate bipolar transistor so that the insulated-gatebipolar transistor turns on when the first voltage is equal to orsmaller than the second over current threshold in a case where the firstvoltage decreases. The driving signal is further input from the externalunit into the diode Schmitt unit. The diode Schmitt unit provides afirst diode current threshold, which defines whether the diode elementpasses current, and a second diode current threshold, which is largerthan the first diode current threshold. The diode Schmitt unit comparesa second voltage between two ends of the second sensing resistor withthe first diode current threshold when the second voltage decreases. Thediode Schmitt unit passes the driving signal to the gate of theinsulated-gate bipolar transistor so that the insulated-gate bipolartransistor turns on when the second voltage is equal to or larger thanthe first diode current threshold in a case where the second voltagedecreases. The diode Schmitt unit stops passing the driving signal tothe gate of the insulated-gate bipolar transistor so that theinsulated-gate bipolar transistor turns off when the second voltage issmaller than the first diode current threshold in a case where thesecond voltage decreases. The diode Schmitt unit compares the secondvoltage with the second diode current threshold when the second voltageincreases. The diode Schmitt unit stops passing the driving signal tothe gate of the insulated-gate bipolar transistor so that theinsulated-gate bipolar transistor turns off when the second voltage issmaller than the second diode current threshold in a case where thesecond voltage increases, and the diode Schmitt unit passes the drivingsignal to the gate of the insulated-gate bipolar transistor so that theinsulated-gate bipolar transistor turns on when the second voltage isequal to or larger than the second diode current threshold in a casewhere the second voltage increases.

In the above device, an increase in a forward loss in the diode can beprevented, and a chattering by the IGBT can be prevented. Moreover,since a current flowing into the IGBT sensing element and a currentflowing into the diode element are sensed by the different sensingresistors, the thresholds can be designed according to the outputcharacteristics of the IGBT sensing element and diode sensing element.

According to a seventh aspect of the present disclosure, a semiconductordevice includes: a semiconductor substrate having a first conductivitytype, having a first principal surface and a second principal surface,and including a main region and a sensing region, wherein an area of thesensing region on the first principal surface is smaller than the mainregion; a diode-built-in insulated-gate bipolar transistor having aninsulated-gate bipolar transistor and a free wheel diode, which aredisposed in the main region of the substrate, wherein the insulated-gatebipolar transistor has a gate electrode, and is driven with a drivingsignal input into the gate electrode; and a diode current sensingelement disposed in the sensing region of the substrate. The free wheeldiode includes a FWD anode having a second conductive type and a FWDcathode having the first conductive type. The FWD anode is provided by afirst surface portion of the main region in the substrate on the firstprincipal surface, and provides a base of the insulated-gate bipolartransistor. The FWD cathode is disposed in a second surface portion ofthe main region in the substrate on the second principal surface. Theinsulated-gate bipolar transistor includes a collector disposed in athird surface portion of the main region in the substrate on the secondprincipal surface, which is different from the second surface portion.The diode current sensing element includes a sensing element anodehaving the second conductive type. The sensing element anode is disposedin a fourth surface portion of the sensing region in the substrate onthe first principal surface, and the diode current sensing elementpasses current in proportion to current flowing through the free wheeldiode.

In the above device, an increase in a forward loss caused by the FWDdiode can be effectively suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription made with reference to the accompanying drawings. In thedrawings:

FIG. 1 is a circuit diagram of a semiconductor device in accordance witha first embodiment;

FIG. 2 shows the relationship among the potential difference Vs betweenthe terminals of a sense resistor, a diode current sensing thresholdVth1, an over current sensing threshold Vth2, and an output of afeedback circuit which is established in the first embodiment;

FIG. 3 is a circuit diagram of a semiconductor device in accordance witha second embodiment;

FIG. 4 shows the relationship among the potential difference Vs betweenthe terminals of a sense resistor, a first diode current sensingthreshold Vth1, a second diode current sensing threshold Vth1′, an overcurrent sensing threshold Vth2, and an output of a feedback circuitwhich is established in the second embodiment;

FIG. 5A is an overall illustrative diagram of a semiconductor chip inaccordance with a third embodiment, and FIG. 5B is a circuit diagram ofa semiconductor device stored in the semiconductor chip shown in FIG.5A;

FIG. 6A is an overall illustrative diagram of a semiconductor chip inaccordance with a fourth embodiment, and FIG. 6B shows the structure ofthe back of the semiconductor chip shown in FIG. 6A;

FIG. 7 is a circuit diagram of a semiconductor device in accordance witha fifth embodiment;

FIG. 8 shows the relationship among the potential difference Vs betweenthe terminals of a sense resistor, a diode current sensing thresholdVth1, and an output of a feedback circuit which is established in thefifth embodiment;

FIG. 9 is a plan view of a semiconductor chip in accordance with a sixthembodiment;

FIG. 10 is a circuit diagram of a semiconductor device in accordancewith the sixth embodiment;

FIG. 11 shows the relationship among the potential difference Vs betweenthe terminals of a sense resistor, a first diode current sensingthreshold Vth1, a second diode current sensing threshold Vth1′, and anoutput of a feedback circuit which is established in the sixthembodiment;

FIG. 12 shows the relationship among the potential difference Vs betweenthe terminals of a sense resistor, a first diode current sensingthreshold Vth1, a third diode current sensing threshold Vth1″, and anoutput of a feedback circuit which is established in a seventhembodiment;

FIG. 13 is a circuit diagram of a semiconductor device in accordancewith an eighth embodiment;

FIG. 14 is a circuit diagram of a semiconductor device in accordancewith a ninth embodiment;

FIG. 15 shows the relationship between a current flowing into diodeelements and a potential difference Vs occurring between the terminalsof a sense resistor;

FIG. 16A shows an output of a first feedback circuit with respect to agate potential Vg outputted from an AND circuit;

FIG. 16B shows an output of a second feedback circuit with respect tothe potential difference Vs;

FIG. 17 is a circuit diagram of a semiconductor device in accordancewith a tenth embodiment;

FIG. 18A shows an output of an IGBT feedback circuit with respect to apotential difference Vs;

FIG. 18B shows an output of a diode Schmitt circuit with respect to thepotential difference Vs;

FIG. 19 is a circuit diagram of a semiconductor device in accordancewith a eleventh embodiment;

FIG. 20A shows an output of an IGBT sensing feedback circuit withrespect to a potential difference Vs1;

FIG. 20B shows an output of a diode sensing Schmitt circuit with respectto a potential difference Vs2;

FIG. 21 is a plan view of a semiconductor chip in accordance with atwelfth embodiment;

FIG. 22 is a plan view showing the outline construction of asemiconductor device in accordance with a thirteenth embodiment;

FIG. 23 is a sectional view along an XXIII-XXIII cutting-plane line inFIG. 22;

FIG. 24 shows an example of a feedback circuit to which thesemiconductor device is adapted;

FIG. 25 shows the relationship among the potential difference Vs betweenthe terminals of a sense resistor, a diode current sensing thresholdVth1, an over current sensing threshold Vth2, and an output of afeedback unit;

FIG. 26 is a sectional view showing the outline construction of asemiconductor device in accordance with a fourteenth embodiment;

FIG. 27 is a sectional view showing a variant;

FIG. 28 is a sectional view showing the outline construction of asemiconductor device in accordance with fifteenth embodiment; and

FIG. 29 is a plan view showing another variant.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

A first embodiment of the present disclosure will be described belowwith reference to the drawings. A semiconductor device of the presentembodiment is used as a power switching device (which may be called aninsulated-gate bipolar transistor (IGBT) device with a body diode) to beincorporated in an inverter module for electric and hybrid vehicles(EHVs).

FIG. 1 is a circuit diagram of the semiconductor device in accordancewith the present embodiment. As shown in the drawing, the semiconductordevice includes an AND circuit 10, an IGBT 20 with a body diode, a senseresistor 30, and a feedback circuit 40.

The AND circuit 10 is a logic circuit that when all inputted signalshave a high level, outputs a high-level signal, and is a so-called ANDgate. An external pulse-width-modulated (PWM) gate signal with which theIGBT 20 with a body diode is driven, and an output of the feedbackcircuit 40 are inputted to the AND circuit 10. Incidentally, the PWMgate signal is produced by an external PWM signal generation circuit orthe like, and is applied to the input terminal of the AND circuit 10.Moreover, the PWM gate signal is equivalent to a driving signal.

The IGBT 20 with a body diode includes an IGBT part 21 and a diode part22. The IGBT 20 with a body diode has the IGBT part 21 and diode part 22formed in the same semiconductor substrate.

The IGBT part 21 includes IGBT elements 21 a for main cells that areconnected to a load or the like, and IGBT sensing elements 21 b forcurrent detection cells that are used to detect a current flowing intothe main-cell IGBT elements 21 a. The IGBT elements 21 a and IGBTsensing elements 21 b are formed to have the same structure. A currentproportional to a current flowing into the IGBT elements 21 a flows intothe IGBT sensing elements 21 b. The IGBT elements 21 a and IGBT sensingelements 21 b are formed to have, for example, a trench gate structure,and have the gates thereof formed in common.

Incidentally, as the IGBT elements 21 a and IGBT sensing elements 21 b,for 30, example, elements each having a trench gate structure thatincludes a trench, a gate insulating film, and a gate electrode may beadopted. Specifically, p-type base regions that are defined as channelregions are formed in the superficial part of an n-type drift layer,n+-type source regions are formed in the superficial parts of therespective p-type base regions, and trenches are formed to penetratethrough the n+-type source regions and p-type base regions so as toreach an n−-type drift layers. Further, gate insulating films made ofSiO2 and gate electrodes made of a poly silicon are sequentially formedon the internal walls of the respective trenches.

The gate voltages of the main-cell IGBT elements 21 a and of thecurrent-detection cell IGBT sensing elements 21 b are controlled basedon a pulse-width-modulated (PWM) gate signal having passed through theAND circuit 10. Specifically, for example, when the PWM gate signalpermitted to pass through the AND circuit 10 is a high-level signal, theIGBT elements 21 a can be turned on in order to drive them. When the PWMgate signal is a low-level signal, the IGBT elements 21 a can be turnedoff in order to cease driving them. On the other hand, when the passageof the PWM gate signal through the AND circuit 10 is ceased, the IGBTelements 21 a and IGBT sensing elements 21 b are not driven.

Moreover, a load or a power supply that is not shown is connected to thecollectors of the IGBT elements 21 a, and a main current flows betweenthe collectors of the IGBT elements 21 a and the emitters thereof. Thecollectors of the IGBT sensing elements 21 b on the current detectioncell sides are formed in common with the collectors of the IGBT elements21 a on the main cell sides, and the emitters of the IGBT sensingelements 21 a on the current detection cell sides are connected to oneof the terminals of the sense resistor 30. The other terminal of thesense resistor 30 is connected to the emitters of the IGBT elements 21a. Consequently, a sense current for current detection that flows fromthe emitters of the IGBT sensing elements 21 b on the current detectioncell sides, that is, a current proportional to a current that flows intothe main-cell IGBT elements 21 a flows into the sense resistor 30, andthe potential difference Vs between the terminals of the sense resistor30 is fed back to the feedback circuit 40.

The diode part 22 is intended to commutate a load current that flowsinto the IGBT elements 21 a, and includes diode elements 22 a for maincells that are connected to the IGBT elements 21 a, and diode sensingelements 22 b for current detection cells that are used to detect acurrent flowing into the main-cell diode elements 22 a. The cathodes ofthe main-cell diode elements 22 a and current-detection cell diodesensing elements 22 b are formed in common.

The anodes of the diode elements 22 a included in the diode part 22 areconnected to the emitters of the IGBT elements 21 a, and the anodes ofthe diode sensing elements 22 b are connected to one of the terminals ofthe sense resistor 30. The cathodes of the diode elements 22 a and diodesensing elements 22 b are connected to the collectors of the IGBTelements 21 a.

Incidentally, as the diode elements 22 a and diode sensing elements 22b, for example, elements having numerous trench gate structures, whichare identical to those of the IGBT part 21, formed in the superficialpart of the semiconductor substrate, and having n+-type regions formedin the back of an n-type silicon substrate may be adopted. In thisconstruction, p-type base regions and n-type drift layers included inthe IGBT part 21 can function as a pn diode.

The feedback circuit 40 decides whether a current has flowed into thediode elements 22 a or whether an over current has flowed into the IGBTelements 21 a. Based on the result of the decision, the feedback circuit40 permits or ceases passage of the PWM gate signal that is inputted tothe AND circuit 10. Therefore, the feedback circuit 40 has a diodecurrent sensing threshold Vth1 that is used to decide whether a currenthas flowed into the diode elements 22 a, and an over current sensingthreshold Vth2 that is used to decide whether an over current has flowedinto the IGBT elements 21 a. In the present embodiment, the diodecurrent sensing threshold Vh1 and over current sensing threshold Vth2are set to voltage values.

If the IGBT elements 21 a are normally driven, that is, if no currentflows into the diode elements 22 a, a current flows from the IGBTsensing elements 21 b to the sense resistor 30. Assuming that thepotential at the emitters of the IGBT elements 21 a is regarded as areference, the potential difference Vs between the terminals of thesense resistor 30 has a positive value. In contrast, if a current flowsinto the diode elements 22 a, a current flows from the sense resistor 30to the diode sensing elements 22 b. Assuming that the potential at theemitters of the IGBT elements 21 a is regarded as a reference, thepotential difference Vs between the terminals of the sense resistor 30becomes negative. Consequently, the diode current sensing threshold Vth1is set to a negative value in order to detect whether a current hasflowed into the diode elements 22 a.

On the other hand, when the IGBT elements 21 a are normally driven, thepotential difference Vs between the terminals of the sense resistor 30assumes, as mentioned above, a positive value. However, if over currentflows into the IGBT elements 21 a, since the value of a sense currentflowing from the IGBT sensing elements 21 b to the sense resistor 30increases, the over current sensing threshold Vth2 is set to a positivevalue.

For driving the IGBT elements 21 a, the feedback circuit 40 outputs asignal with which the passage of the PWM gate signal to be inputted tothe AND circuit 10 is permitted, and inputs the potential difference Vsbetween the terminals of the sense resistor 30. If the potentialdifference Vs is smaller than the diode current sensing threshold Vth1or is larger than the over current sensing threshold Vth2, the feedbackcircuit 40 outputs a signal with which the passage of the PWM gatesignal to be inputted to the AND circuit 10 is ceased. Moreover, thefeedback circuit 40 is formed with a combination of, for example,operational amplifiers or the like. The overall configuration of thesemiconductor device in accordance with the present embodiment has beendescribed so far.

Incidentally, the AND circuit 10, sense resistor 30, and feedbackcircuit 40 are equivalent to a feedback means or a feedback unit.

Next, the actions in the semiconductor device will be described withreference to FIG. 2. FIG. 2 shows the relationship among the potentialdifference Vs between the terminals of the sense resistor 30, the diodecurrent sensing threshold Vth1, the over current sensing threshold Vth2,and the output of the feedback circuit 40. IIA represents a region inwhich the potential difference Vs equal to or smaller than the diodecurrent sensing threshold Vth1, and shows that diode current is detectedso that a passage of a gate signal is ceased. IIB represents a region inwhich the potential difference Vs equal to or larger than the overcurrent sensing threshold Vth2, and shows that over current is detectedso that a passage of a gate signal is ceased. To begin with, the normalactions in the semiconductor device will be described below.

A PWM gate signal is produced as a driving signal, with which the IGBTelements 21 a of the semiconductor device are driven, by a PWM signalgeneration circuit or any other external circuit, and is inputted to theAND circuit 10. On the other hand, the diode elements 22 a are left off,and no current flows into the diode sensing elements 22 b. Consequently,the potential at one of the terminals of the sense resistor 30 that isconnected to the IGBT sensing elements 21 b gets higher than thepotential at the other terminal thereof connected to the emitters of theIGBT elements 21 a. Consequently, the potential difference Vs betweenthe terminals of the sense resistor 30 assumes a positive value with thepotential at the emitters of the IGBT elements 21 a as a reference.

Consequently, as shown in FIG. 2, the potential difference Vs is largerthan the negative diode current sensing threshold Vth1. The feedbackcircuit 40 decides that no current has flowed into the diode elements 22a. Consequently, the output of the feedback circuit 40 is, as shown inFIG. 2, set to a high level, and inputted to the AND circuit 10. Whenthe high-level PWM gate signal and the output of the feedback circuit 40are inputted to the AND circuit 10, the PWM gate signal is permitted topass through the AND circuit 10 and inputted to the IGBT part 21. TheIGBT part 21 is therefore turned on. Thus, the IGBT elements 21 a aredriven, and a current flows into the load that is not shown and isconnected to the collectors or emitters of the IBGT elements 21 a.

When a current flows into the diode elements 22 a, since the potentialat the other one of the terminals of the sense resistor 30 which isconnected to the emitters of the IGBT elements 21 a gets higher than thepotential at one of the terminals thereof connected to the emitters ofthe IGBT elements 21 b, the potential difference Vs between theterminals of the sense resistor 30 becomes negative with the potentialat the emitters of the IGBT elements 21 a as a reference.

Consequently, when the potential difference Vs is smaller than the diodecurrent sensing threshold Vth1, the feedback circuit 40 decides that acurrent has flowed into the diode elements 22 a. The output of thefeedback circuit 40 is therefore an output with which the passage of thePWM gate signal to be inputted to the AND circuit is ceased, and isinputted to the AND circuit 10.

Since a signal with which the IGBT part 21 is driven is not inputtedfrom the AND circuit 10, driving the IGBT elements 21 a is ceased. Inother words, when the diode elements 22 a act in a forward direction,the IGBT elements 21 a do not act.

As long as the IGBT elements 21 a and diode elements 22 a are formed inthe same semiconductor substrate, such an incident will not occur thatwhen the diode elements 22 a act in the forward direction, if thechannels of the IBGT elements 21 a conduct, the anodes and cathodes ofthe diode elements 22 a are brought to the same potential. The diodeelements 22 a will therefore not be able to readily act in the forwarddirection due to the gate potential of the IGBT elements 21 a. In otherwords, the interference between the action of the diode elements 22 aand the action of the IGBT elements 21 a, or more particularly, theinterference between the potential at the diode elements 22 a and thegate signal for the IGBT elements 21 a can be avoided. Consequently,since an increase in the forward voltage of the diode elements 22 a canbe avoided, an increase in a loss in the forward voltage of the diodeelements 22 a can be prevented.

On the other hand, if an over current flows into the IGBT elements 21 a,a sense current that flows from the IGBT sensing elements 21 b to thesense resistor 30 increases proportionally to the over current. When theIGBT elements 21 a normally act, the potential difference Vs gets higherthan the potential difference Vs attained when a current flows into theIGBT elements 21 a.

Consequently, when the potential difference Vs gets larger than the overcurrent sensing threshold Vth2, the feedback circuit 40 decides that anover current has flowed into the IGBT elements 21 a. Eventually, asmentioned above, the passage of the PWM gate signal to be inputted tothe AND circuit 10 is ceased with the output of the feedback circuit 40,and driving the IGBT elements 21 a is ceased. Thus, the IGBT elements 21a can be protected from being broken with the over current that flowsinto the IGBT elements 21 a.

As mentioned above, in the present embodiment, the diode current sensingthreshold Vth1 and over current sensing threshold Vth2 are defined.Therefore, if the potential difference Vs between the terminals of thesense resistor 30 is equal to or larger than the diode current sensingthreshold Vth1 and equal to or smaller than the over current sensingthreshold Vth2 with the potential at the emitters of the IGBT elements21 a regarded as a reference, the output of the feedback circuit 40 isan output with which the passage of the PWM gate signal to be inputtedto the AND circuit 10 is ceased.

As mentioned above, in the present embodiment, a current flowing intothe diode elements 22 a is sensed by the diode sensing elements 22 b andsense resistor 30. In other words, whether a current has flowed into thediode elements 22 a is decided by monitoring the potential difference Vsbetween the terminals of the sense resistor 30 connected to the IGBTsensing elements 21 b. Based on the result of the decision, the outputof the feedback circuit 40 is used to permit or cease the passage of thePWM gate signal to be inputted to the AND circuit 10.

Consequently, if a current flows into the diode elements 22 a, drivingthe IGBT elements 21 a is ceased, that is, the passage of the PWM gatesignal to be inputted to the AND circuit 10 is ceased, and the IGBTelements 21 a is stopped.

Therefore, the action of the IGBT elements 21 a and the action of thediode elements 22 a can be prevented from being interfered with eachother. Consequently, an increase in the forward voltage Vf of the diodeelements 22 a occurring when the IGBT elements 21 a act along with theaction of the diode elements 22 a can be prevented. Eventually, anincrease in a forward loss derived from the increase in the forwardvoltage Vf of the diode elements 22 a can be prevented.

Moreover, the feedback circuit 40 senses a current, which flows into thesense resistor 30, so as to thus decide whether an over current hasflowed into the IGBT elements 21 a. If the feedback circuit 40 decidesthat the over current has flowed into the IGBT elements 21 a, drivingthe IGBT elements 21 a can be ceased. The IGBT elements 21 a cantherefore be protected from being broken.

Further, since the semiconductor device is constructed by adopting theAND circuit 10, sense resistor 30, and feedback circuit 40, the elementstructure of the IGBT 20 with a body diode need not be modified and thechip size need not be increased.

Second Embodiment

In the present embodiment, the temperature of a semiconductor device isdetected, and the diode current sensing threshold Vth1 is changed toanother on the basis of the detected temperature.

FIG. 3 is a circuit diagram of a semiconductor device in accordance withthe present embodiment. As shown in the drawing, the semiconductordevice in accordance with the present embodiment has temperaturesensitive diode elements 50 added to the construction shown in FIG. 1.

The temperature sensitive diode elements 50 are used to measure thetemperature of the semiconductor device, or more particularly, thetemperature of the IGBT 20 with a body diode. The temperature sensitivediode elements 50 output temperature-dependent voltages, that is, havethe forward voltages thereof varied, and output forward voltagesdependent on heat dissipated along with the action of the IGBT 20 with abody diode.

The temperature sensitive diode elements 50 are constructed by, forexample, forming polysilicon layers as n-type layers or p-type layers oninsulating films formed on a semiconductor substrate. As shown in FIG.3, the present embodiment adopts a circuit form in which: fourtemperature sensitive diode elements 50 are connected in series with oneanother; and a total forward voltage Vm of the temperature sensitivediode elements 50 that is a forward voltage with respect to a ground isinputted to the feedback circuit 40.

A constant current flows from the feedback circuit 40 to the temperaturesensitive diode elements 50. As mentioned above, the forward voltage Vmof the temperature sensitive diode elements 50 that varies depending ontemperature is inputted to the feedback circuit 40.

Moreover, in the present embodiment, the feedback circuit 40 has twodiode current sensing thresholds Vth1 and Vth1′. Hereinafter, thethreshold Vth1 shall be called a first diode current sensing threshold,and the threshold Vth1′ shall be called a second diode current sensingthreshold. The second diode current sensing threshold Vth1′ is set to alarger value than the first diode current sensing threshold Vth1 is.

Further, if the feedback circuit 40 decides that the forward voltage Vmoutputted from the temperature sensitive diode elements 50 exceeds atemperature threshold indicating the high-temperature state of the IGBT20 with a body diode, the feedback circuit 40 compares the potentialdifference Vs between the terminals of the sense resistor 30 with thesecond diode current sensing threshold Vth1′ but does not compare thepotential difference Vs with the first diode current sensing thresholdVth1.

Specifically, when the IGBT 20 with a body diode enters thehigh-temperature state, the feedback circuit 40 makes it easier todecide whether a current has flowed into the diode elements 22 airrespective of however microscopic the current flowing into the diodeelements 22 a is. Consequently, even when the microscopic current flowsinto the diode elements 22 a, the feedback circuit 40 ceases driving theIGBT elements 21 a so as to suppress heat dissipation from the IGBT 20with a body diode.

Next, referring to FIG. 4, the actions in the semiconductor device to beperformed when the IGBT 20 with a body diode enters the high-temperaturestate will be described below. FIG. 4 shows the relationship among thepotential difference Vs between the terminals of the sense resistor 30,the first diode current sensing threshold Vth1, the second diode currentsensing threshold Vth1′, the over current sensing threshold Vth2, andthe output of the feedback circuit 40. IVA represents a region in whichthe potential difference Vs equal to or smaller than the diode currentsensing threshold Vth1, and shows that diode current is detected so thata passage of a gate signal is ceased. IVB represents a region in whichthe potential difference Vs equal to or larger than the over currentsensing threshold Vth2, and shows that over current is detected so thata passage of a gate signal is ceased.

Similarly to the first embodiment, when both the PWM gate signal and theoutput of the feedback circuit 40 are inputted to the AND circuit 10,the passage of the PWM gate signal to be inputted to the AND circuit 10is permitted, and the IGBT elements 21 a are driven. In this case, theforward voltage Vm dependent on the temperature of the IGBT 20 with abody diode is detected by the temperature sensitive diode elements 50,and is inputted to the feedback circuit 40.

If the feedback circuit 40 decides that the forward voltage Vm inputtedfrom the temperature sensitive diode elements 50 exceeds a temperaturethreshold, the first diode current sensing threshold Vth1 is, as shownin FIG. 4, changed to the second diode current sensing threshold Vth1′.

Consequently, although the sense current flowing into the sense resistor30 is smaller than that detected when the potential difference Vs iscompared with the first diode current sensing threshold Vth1, the flowof the current into the diode elements 22 a can be decided.

When the potential difference Vs between the terminals of the senseresistor 30 gets smaller than the second diode current sensing thresholdVth1′, the feedback circuit 40 decides that a current has flowed intothe diode elements 22 a. Driving the IGBT elements 21 a is, similarly tothat in the first embodiment, ceased.

As mentioned above, when the temperature of the IGBT 20 with a bodydiode gets high, a criterion for deciding whether a current has flowedinto the diode elements 22 a is changed from one to another. This makesit easier to decide whether a current has flowed into the diode elements22 a. Consequently, even when a current flowing into the diode elements22 a has a small current value, the interference of the gate signal forthe IGBT elements 21 a with the potential at the diode elements 22 a canbe prevented. Further, since driving the IGBT elements 21 a is ceased,heat dissipation of the IGBT 20 with a body diode can be suppressed.

Third Embodiment

In the second embodiment, the components are constructed as independentparts. In the present embodiment, the components of the secondembodiment are integrated into one chip.

FIG. 5A is an overall illustrative diagram of a semiconductor chip 60 inaccordance with the present embodiment. FIG. 5B is a circuit diagram ofa circuit included in the semiconductor chip 60 and is identical to thecircuit diagram of FIG. 3.

As shown in FIG. 5A, the semiconductor chip 60 includes an IGBT 20 witha body diode, temperature sensitive diode elements 50, a processingcircuit unit 70, current sensing elements 61, a gate pad 62, and a guardring 63.

The processing circuit unit 70 shown in FIG. 5A includes a feedbackcircuit 40, an AND circuit 10, and a sense resistor 30 which are shownin FIG. 5B. The feedback circuit 40 is formed with, for example, athin-film transistor circuit.

Moreover, the current sensing elements 61 sense currents that flow intoIGBT elements 21 a and diode elements 22 a respectively, and includesdiode sensing elements 22 b and IGBT sensing elements 21 b. In thepresent embodiment, the diode sensing elements 22 b are not included inthe IGBT 20 with a body diode, and the current sensing elements 61detects a current flowing into the diode elements 21 a. In the presentembodiment, the current sensing elements 61 sense both the currents thatflow into the IGBT elements 21 a and diode elements 22 a respectively.When the current sensing elements 61 are said to sense both thecurrents, it means that the current sensing elements 61 can detect boththe current flowing into the diode elements 22 a and the current flowinginto the IGBT elements 21 a.

The temperature sensitive diode elements 50 are disposed, for example,in the center of the semiconductor chip 60. Since the temperature of thecenter of the semiconductor chip 60 becomes highest because heatdissipated when the semiconductor chip 60 is put into action isconcentrated on the center of the semiconductor chip 60, the temperaturesensitive diode elements 50 are disposed in the center of thesemiconductor chip 60.

The gate pad 62 is an electrode which is connected to the input terminalof the AND circuit 10 and to which a PWM gate signal is externallyapplied.

The guard ring 63 surrounding the IGBT 20 with a body diode, temperaturesensitive diode elements 50, processing circuit unit 70, current sensingelements 61, and gate pad 62 is disposed on the perimeter of thesemiconductor chip 60. The guard ring 63 fills the role of ensuring thedielectric strength of the semiconductor chip 60.

As mentioned above, when the semiconductor device is incorporated in thesemiconductor chip 60, a general-purpose circuit can be adopted as a PWMcontrol circuit that is used to drive the IGBT part 21.

Fourth Embodiment

FIG. 6A is an overall illustrative diagram of a semiconductor chip 60 inaccordance with the present embodiment. FIG. 6B shows the structure ofthe back of the semiconductor chip 60 shown in FIG. 6A. Thesemiconductor chip 60 shown in FIG. 6A includes, similarly to that ofthe third embodiment, a semiconductor device shown in the circuitdiagram of FIG. 5B.

As shown in FIG. 6A, in the present embodiment, unlike the thirdembodiment, the diode sensing elements 22 b and IGBT sensing elements 21b are incorporated in the semiconductor chip 60 independently of eachother.

As shown in FIG. 6B, the semiconductor chip 60 is formed in an n-typesubstrate 80. In the back of the semiconductor chip 60, p+-type regions81 realizing the IGBT part 21 and n+-type region 82 realizing the diodepart 22 are alternately repeatedly disposed.

Normally, since only the p+-type regions 81 are formed in the back of achip in the IGBT sensing elements 21 b, a current flows into the IGBTsensing elements 21 b but a current hardly flows into the diode sensingelements 22 b. However, in the present embodiment, since the n+-typeregion 82 s are disposed together with the p+-type regions 81 (both-sidealignment), the output of the diode sensing elements 22 b can beincreased. Eventually, the current detecting sensitivity can beintensified.

Fifth Embodiment

In the first to fourth embodiments, the IGBT 20 with a body diode isadopted as a switching device. In the present embodiment, adouble-diffused metal-oxide FET semiconductor (DMOS) is adopted.

Specifically, sensing elements incorporated in the DMOS are used tosense the polarity of a current flowing into diode elements so that adiode action will be realized with a DMOS action. During a time duringwhich the diode elements act in a forward direction, a gate signal forDMOS elements is brought to an on-state voltage level so that a currentoriented in the same direction as the direction of a current flowinginto the diode elements will flow into the DMOS elements. Thus, acurrent is prevented from flowing into the diode elements in which aforward voltage is developed. Eventually, an increase in a dc loss inthe diode elements is prevented.

FIG. 7 is a circuit diagram of a semiconductor device in accordance withthe present embodiment. As shown in the drawing, the semiconductordevice includes a DMOS 100 with a body diode, a sense resistor 30, and afeedback circuit 200. Connection forms of the DMOS 100 with a body diodeand the sense resistor 30 are identical to those shown in FIG. 1.

The DMOS 100 with a body diode includes a DMOS part 110 and a diode part120. The DMOS 100 with a body diode has the DMOS part 110 and diode part120 formed in the same semiconductor substrate.

The DMOS part 110 includes DMOS elements 111 for main cells that areconnected to a load or the like, and DMOS sensing elements 112 forcurrent detection cells that are used to detect a current flowing intothe main-cell DMOS elements 111. The DMOS elements 111 and DMOS sensingelements 112 are formed to have the same structure. The currentproportional to the current flowing into the DMOS elements 111 flowsinto the DMOS sensing elements 112. The gate voltages in the main-cellDMOS elements 111 and current-detection cell DMOS sensing elements 112are controlled by the feedback circuit 200.

The diode part 120 includes diode elements 121 for main cells that areconnected to the DMOS elements 111, and diode sensing elements 122 forcurrent detection cells that are used to detect a current flowing intothe main-cell diode elements 121.

The feedback circuit 200 inputs the potential difference Vs that occursbetween the terminals of the sense resistor 30 when a current flows intothe main-cell DMOS elements 111, decides based on the potentialdifference Vs whether a current has flowed into the diode elements 121,and controls driving of the DMOS elements 111 on the basis of the resultof the decision. Therefore, the feedback circuit 200 has a diode currentsensing threshold Vth1 to be used to decide whether a current has flowedinto the diode elements 121. The diode current sensing threshold Vth1 isset to, for example, a voltage value. Similarly to the first embodiment,the diode current sensing threshold Vth1 is set to a negative value inorder to detect whether a current has flowed into the diode elements121. Incidentally, the feedback circuit 200 is put into action whenapplied a voltage from a power supply 300.

Next, the actions in the semiconductor device will be described withreference to FIG. 8. FIG. 8 shows the relationship among the potentialdifference Vs between the terminals of the sense resistor 30, the diodecurrent sensing threshold Vth1, and the output of the feedback circuit200. VIII represents a region in which the potential difference Vs equalto or smaller than the diode current sensing threshold Vth1, and showsthat diode current is detected so that a passage of a gate signal ispermitted.

To begin with, at the timing at which the diode elements 121 act in asynchronous rectification mode, current flows in a forward directioninto the diode elements 121, that is, from the anodes of the diodeelements 121 to the cathodes thereof. Accordingly, a current also flowsinto the diode sensing elements 122. A potential difference thereforeoccurs in the sense resistor 30 connected to the diode sensing elements122.

Specifically, when a forward current flows into the diode elements 121,the potential at the other terminal of the sense resistor 30 which isconnected to the sources of the DMOS elements 111 gets higher than thepotential at one terminal thereof connected to the sources of the DMOSsensing elements 112. The potential difference Vs between the terminalsof the sense resistor 30 therefore has a negative value with thepotential at the sources of the DMOS elements 111 regarded as areference. The negative potential difference Vs is inputted to thefeedback circuit 200, and compared with the negative diode currentsensing threshold Vth1. If the potential difference Vs has a largernegative value than the diode current sensing threshold Vth1 does, thefeedback circuit 200 produces a gate signal (high level) with which theDMOS elements 111 are turned on, and the DMOS elements 111 are thenturned on.

When a current flows into the diode elements 121, a forward voltage Vfis required. This causes a dc loss to occur in a circuit in which thesemiconductor device is incorporated. However, when the DMOS elements111 are turned on, the DMOS elements 111 function as wiring (resistiveelements). Therefore, a current flows from the sources of the DMOSelements 111 to the drains thereof but no current flows into the diodeelements 121. In other words, the feedback circuit 200 turns on the DMOSelements 111 so that a current oriented in the same direction as thedirection in which the forward current of the diode elements 121 flowswill flow into the DMOS elements 111. Thus, the current that has flowedin a forward direction into the diode elements 121 flows into the DMOSelements 111. Consequently, an increase in a loss in the forward voltageVf needed to cause the forward current to flow into the diode elements121 is prevented.

On the other hand, an operation of rectification is exerted in the diodeelements 121. At the timing at which a current oriented in an oppositedirection flows into the diode elements 121, the potential at one of theterminals of the sense resistor 30 which is connected to the DMOSsensing elements 112 gets higher than the potential at the otherterminal thereof connected to the sources of the DMOS elements 111. Thepotential difference Vs between the terminals of the sense resistor 30has a positive value with the potential at the sources of the DMOSelements 111 regarded as a reference. If the feedback circuit 200decides that the value of the positive potential difference Vs is largerthan the value of the negative diode current sensing threshold Vth1, agate signal (low level) with which the DMOS elements 111 are turned offis, as shown in FIG. 8, produced. The DMOS elements 111 are turned offby the feedback circuit 200. Thus, when the operation of rectificationis exerted in the diode elements 121, the DMOS elements 111 are turnedoff.

As mentioned above, according to the present embodiment, in thesemiconductor device employing the DMOS 100 with a body diode, when aforward current flows into the diode elements 121, the DMOS elements 111are turned on so that a current will flow into the DMOS elements 111.Consequently, when the forward current flows into the diode elements121, a loss in the forward voltage Vf developed in the diode elements121 will not occur. A low-loss switching action can be achieved.

Sixth Embodiment

In the present embodiment, the circuit shown in FIG. 7 and presented asthe fifth embodiment detects the temperature of a semiconductor device.Similarly to that in the second embodiment, the diode current sensingthreshold Vth1 is changed to another on the basis of the detectedtemperature.

FIG. 9 is a plan view of a semiconductor chip 60 of the presentembodiment. As shown in FIG. 9, the semiconductor chip 60 includes aDMOS 100 with a body diode, temperature sensitive diode elements 50, aprocessing circuit unit 71, current sensing elements 61, a gate pad 62,a guard ring 63, a source pad 64, and a power supply pad 65.

The source pad 64 is an electrode connected to a load. The power supplypad 65 is an electrode for use in applying a voltage from a power supplyto a feedback circuit 200. Assuming that the surface of thesemiconductor chip 60 shown in FIG. 9 is the face thereof, a drain padis disposed on the back of the semiconductor chip 60. FIG. 10 shows anequivalent circuit of the construction.

In FIG. 10, the processing circuit unit 71 includes the feedback circuit200 and a sense resistor 30. Moreover, the temperature sensitive diodeelements 50 shown in FIG. 3 are connected to the feedback circuit 200. Aconstant current flows from the feedback circuit 200 to the temperaturesensitive diode elements 50. As mentioned previously, the forwardvoltage Vm of the temperature sensitive diode elements 50 that variesdepending on temperature is inputted to the feedback circuit 200.

The feedback circuit 200 has, similarly to that of the secondembodiment, a first diode current sensing threshold Vth1 and a seconddiode current sensing threshold Vth1′ larger than the first diodecurrent sensing threshold Vth1. If the feedback circuit 200 decides thatthe forward voltage vm inputted from the temperature sensitive diodeelements 50 exceeds a temperature threshold indicating thehigh-temperature state of the DMOS 100 with a body diode, the feedbackcircuit 200 compares the potential difference Vs between the terminalsof the sense resistor 30 with the second diode current sensing thresholdVth1′ but does not compare the potential difference Vs with the firstdiode current sensing threshold Vth1.

Specifically, as shown in FIG. 11, when the DMOS 100 with a body diodeenters the high-temperature state, the feedback circuit 200 makes iteasy to decide whether a current has flowed into the diode elements 121irrespective of however microscopic the current flowing into the diodeelements 121 is. Consequently, even when the microscopic current flowsinto the diode elements 121, the feedback circuit 200 drives the DMOSelements 121 a so as to disable a forward current from flowing into thediode elements 121. XI represents a region in which the potentialdifference Vs equal to or smaller than the diode current sensingthreshold Vth1′, and shows that diode current is detected so that apassage of a gate signal is permitted.

As mentioned above, when the semiconductor device operates at the hightemperature at which a loss in the diode elements 121 causes a trouble,the feedback circuit 200 lowers the threshold for use in sensing a diodecurrent. Thus, an increase in a dc loss in even a small current flowinginto the diode elements 121 is prevented, and heat dissipation from thediode elements 121 can be suppressed.

Seventh Embodiment

In the present embodiment, the noise resistivity is improved in order tocope with a case where the potential difference Vs fluctuates due tonoise.

Consequently, the feedback circuit 200 has a diode current sensingthreshold Vth1″ larger than the diode current sensing threshold Vth1.Herein, the diode current sensing threshold Vth1 shall be called a firstdiode current sensing threshold, and the diode current sensing thresholdVth1″ shall be called a third diode current sensing threshold.

As shown in FIG. 12, when the value of the potential difference Vschanges to a negative side, the feedback circuit 200 uses the firstdiode current sensing threshold Vth1 to decide whether the DMOS elements111 should be driven. On the other hand, when the value of the potentialdifference Vs changes to a positive side, the feedback circuit 200 usesthe third diode current sensing threshold Vth1″ to decide whether theDMOS elements 111 should be driven. Thus, the feedback circuit 200 actslike a Schmitt circuit. XII represents a region in which the potentialdifference Vs equal to or smaller than the diode current sensingthreshold Vth1, and shows that diode current is detected so that apassage of a gate signal is permitted.

Consequently, even when the potential difference Vs fluctuates due tonoise, since the first diode current sensing threshold Vth1 and thirddiode current sensing threshold Vth1″ have a noise margin between them,such an incident will not take place that the on and off states of theDMOS elements 111 are switched due to the noise. A semiconductor devicehighly resistant to noise can be realized.

Eighth Embodiment

In the fifth to seventh embodiments, the semiconductor device itselfdiagnoses a current flowing into the diode elements 121 so as to turn onor off the DMOS elements 111 for the purpose of minimizing a dc loss inthe diode elements 121. The DMOS with a body diode functions as a diodein relation to an external circuit. In the present embodiment, the DMOSelements 111 function as switching elements.

FIG. 13 is a circuit diagram of a semiconductor device in accordancewith the present embodiment. As shown in the drawing, the output of thefeedback circuit 200 is inputted to an OR circuit 400. Moreover, aswitching signal with which the DMOS elements 111 are turned on or offis inputted from an external control circuit to the OR circuit 400.

Consequently, when a current flows into the diode elements 121, thefeedback circuit 200 inputs a driving signal, with which the DMOSelements 111 are turned on, to the OR circuit 400. Accordingly, the DMOSelements 111 are turned on. As described in relation to the fifthembodiment, a current flows, as indicated with an arrow 500 in FIG. 3,from the sources of the DMOS elements 111 to the drains thereof. A lossin the forward voltage Vf of the diode elements 121 is minimized.

On the other hand, when the feedback circuit 200 does not sense that acurrent has flowed into the diode elements 121, if the DMOS elements 111are allowed to function as switching elements, the external controlcircuit inputs the switching signal, with which the DMOS elements 111are turned on, to the OR circuit 400. The OR circuit 400 then turns onthe DMOS elements 111. Consequently, a current flows, as indicated withan arrow 600 in FIG. 13, from the drains of the DMOS elements 111 to thesources thereof. The DMOS elements 111 therefore function as theswitching elements.

As mentioned above, the DMOS elements 111 included in the semiconductordevice can be not only used to minimize a dc loss in the diode elements121 but also used as switching elements. The OR circuit 400 isequivalent to a driving means or a driving unit.

Other Embodiments

The embodiments have been described on the assumption that the IGBT part21 is controlled according to a pulse-width modulation (PWM) controlmethod. The PWM control is merely one form of controls. For example, theIGBT elements 21 a may be driven in a full-on mode. The same applies todriving of the DMOS elements 111 included in the eighth embodiment.

In the first to fourth embodiments, the feedback circuit 40 decides botha current flowing into the diode elements 22 a and an over currentflowing into the IGBT elements 21 a. A semiconductor device may bedesigned so that the feedback circuit 40 will decide only the currentflowing into the diode part 22. In this case, the IGBT sensing elements21 b need not be included in the IGBT part 21. The semiconductor devicemay include as the IGBT 20 with a body diode the IGBT elements 21 a andthe diode part 22. Hall-effect elements may be adopted as elements thatdetect current components flowing into the respective diode elements 21a. As for the adoption of the Hall-effect elements, the same applies tothe fifth to eighth embodiments.

Incidentally, the circuitry in which the diode sensing elements 22 b arenot employed but a current that flows into the diode elements 22 a isdirectly detected may be adopted. In this case, a semiconductor deviceshould merely include the IGBT 20 with a body diode, and a means (or aunit) that detects a current flowing into the diode elements 22 a, thatif no current flows into the diode elements 22 a, permits the passage ofan externally inputted pulse-width-modulated (PWM) gate signal, and thatif a current flows into the diode elements 22 a, ceases the passage ofthe PWM gate signal (for example, the AND circuit 10, sense resistor 30,and feedback circuit 40). In this case, the circuitry including thesense resistor 30 in addition to the means or the unit for permitting orceasing the passage of the PWM gate signal will do. Further, thecircuitry in which a current flowing into the diode sensing elements 22b flows into the sense resistor 30 will do. Needless to say, thecircuitry in which the temperature sensitive diode elements 50 arefurther included will do. The circuitry in which the diode sensingelements 122 may not be employed but a current flowing into the diodeelements 121 is directly detected may be adopted in the fifth to eightsembodiments.

In the embodiments, the diode current sensing thresholds Vth1, Vth1′,and Vth1″ are set to negative values, and the over current sensingthreshold Vth2 is set to a positive value. This is a mere example. Thus,it is not limited to the threshold values. Moreover, the diode currentsensing thresholds Vth1, Vth1′, and Vth″ and over current sensingthreshold Vth2 are set to voltage values. In a case where the feedbackmeans including the AND circuit 10, sense resistor 30, and feedbackcircuit 40 detects a current flowing into the diode elements 22 a, thethresholds are set to current values.

For the second and sixth embodiments, as shown in FIG. 3 and FIG. 10,the circuit form in which the four temperature sensitive diode elements50 are directly connected has been introduced. The number of temperaturesensitive diode elements 50 that is four is a mere example. Multipletemperature sensitive diode elements or one temperature sensitive diodeelement may be adopted.

The feedback circuit 200 that is included in the seventh embodiment andfunctions like a Schmitt circuit may be adopted as the feedback circuit200 that is included in the sixth embodiment and senses temperature.

Ninth Embodiment

FIG. 14 is a circuit diagram of a semiconductor device in accordancewith the present embodiment. As shown in the drawing, the circuitryincludes, in addition to the circuits shown in FIG. 1, a first feedbackcircuit 41 and a second feedback circuit 42.

The first feedback circuit 41 is connected between the output terminalof the AND circuit 10 and the second feedback circuit 42. The firstfeedback circuit 41 decides whether the IGBT elements 21 a are turned onor off with a gate signal (gate potential Vg) outputted from the ANDcircuit 10, and outputs the result of the decision to the secondfeedback circuit 42.

To be more specific, the first feedback circuit 41 has a criterialthreshold H0 for the gate signal (gate potential Vg). If the gate signaloutputted from the AND circuit 10 exceeds the criterial threshold H0,the first feedback circuit outputs a first diode current sensingthreshold H1, which signifies that the IGBT elements 21 a have beenturned on, to the second feedback circuit 42. If the gate signal doesnot exceed the criterial threshold H0, the first feedback circuitoutputs a second diode current sensing threshold, which has a largervalue than the first diode current sensing threshold H1 does andsignifies that the IGBT elements 21 a have been turned off, to thesecond feedback circuit 42. The thresholds H1 and H2 are set to negativevalues.

The second feedback circuit 42 compares the potential difference Vs withthe threshold H1 or H2 inputted from the first feedback circuit 41.Based on the result of the decision, the second feedback circuit 42permits or ceases the passage of a pulse-width-modulated (PWM) gatesignal to be inputted to the AND circuit 10. Moreover, the secondfeedback circuit 42 has an over current sensing threshold Vth2 describedin relation to the first embodiment.

As mentioned above, the second feedback circuit 42 compares thepotential difference Vs with either of the different thresholds H1 andH2 according to the gate signal. This is because the magnitude of acurrent flowing into the diode elements 22 a (freewheeling diode (FWD)elements) varies depending on whether the IGBT elements 21 a have beenturned on or off.

FIG. 15 shows the relationship between a current flowing into the diodeelements 22 a and the potential difference Vs between the terminals ofthe sense resistor 30. XVA represents an IGBT action domain, and XVBrepresents a FWD action domain. As indicated in the drawing, when boththe current I flowing into the diode elements 22 a and the potentialdifference Vs have positive values, the current I and potentialdifference Vs have a relationship of proportion. However, when thecurrent flowing into the diode elements 22 a becomes negative, that is,when the diode elements 22 a are put into action, the potentialdifference Vs assumes a different value with respect to the currentvalue according to whether the IGBT elements 21 a have been turned on(Vg=on-state voltage) or off (Vg=off-state voltage). In other words,while ideal current values are plotted as a dashed line in an FWD actiondomain in FIG. 15, different lines are drawn in association with thevalues of the gate potential Vg.

Specifically, when a current has flowed into the diode elements 22 a, ifthe IGBT elements 21 a are turned on, since a current flows from theIGBT sensing elements 21 b to the sense resistor 30, the potentialdifference Vs between the terminals of the sense resistor 30 getslarger. In contrast, when a current has flowed into the diode elements22 a, if the IGBT elements 21 a are turned off, since the potentialdifference Vs in the sense resistor 30 depends on the current flowinginto the diode elements 22 a, the potential difference Vs gets smallerthan that attained when the IGBT elements 21 a are turned on.

Consequently, since either of the different thresholds H1 and H2 is useddepending on whether the IGBT elements 21 a have been turned on or offwhen a current has flowed into the diode elements 22 a, the IGBTelements 21 a can be controlled more stably. According to the thresholdH1 or H2 inputted from the first feedback circuit 41, when the IGBTelements 21 a have been turned on, the second feedback circuit 42compares the potential difference Vs with the first diode currentsensing threshold H1. When the IGBT elements 21 a have been turned off,the second feedback circuit 42 compares the potential difference Vs withthe second diode current sensing threshold H2 smaller than the firstdiode current sensing threshold H1.

In FIG. 15, within an IGBT action domain, when the potential differenceVs has a value Vth3, a current Imax flows into the diode elements 22 a.

Referring to FIG. 16A and FIG. 16B, a description will be made below.FIG. 16A shows an output of the first feedback circuit 41 with respectto the gate potential Vg outputted from the AND circuit 10, and FIG. 16Bshows an output of the second feedback circuit 42 with respect to thepotential difference Vs. In FIG. 16A, the axis of ordinates indicatesnegative values. In FIG. 16B, the axis of ordinates indicates positivevalues.

As shown in FIG. 16A, the first feedback circuit 41 compares the gatepotential Vg outputted from the AND circuit 10 with the criterialthreshold H0 and decides whether the gate potential Vg has a value withwhich the IGBT elements 21 a are driven. If the gate potential Vgexceeds the criterial threshold H0, the first feedback circuit 41outputs the first diode current sensing threshold H1. If the gatepotential Vg falls below the criterial threshold H0, the first feedbackcircuit 41 outputs the second diode current sensing threshold H2.

Thereafter, as indicated by FIG. 16B, the second feedback circuit 42compares the potential difference Vs with either the first diode currentsensing threshold H1 or second diode current sensing threshold H2inputted from the first feedback circuit 41. When the potentialdifference Vs increases from a negative side to a positive side, if thepotential difference Vs exceeds the second diode current sensingthreshold H2, the second feedback circuit permits the PWM gate signal,which is externally inputted to the AND circuit 10, to pass through theAND circuit 10. On the other hand, when the potential difference Vsdecreases from the positive side to the negative side, if the potentialdifference Vs falls below the first diode current sensing threshold H1,the second feedback circuit 42 does not permit the PWM gate signal,which is externally inputted to the AND circuit 10, to pass through theAND circuit 10. The second feedback circuit 42 controls the passage ofthe PWM gate signal through the AND circuit 10 according to the gatepotential Vg of the IGBT elements 21 a so that the passage will have ahysteresis.

Moreover, similarly to the first embodiment, when the potentialdifference Vs between the terminals of the sense resistor 30 is largerthan the over current sensing threshold Vth2, the second feedbackcircuit 42 ceases the passage of the PWM gate signal to be inputted tothe AND circuit 10 so as to protect the IGBT elements 21 a from beingbroken due to an over current.

As mentioned above, in the present embodiment, information on the on oroff state of the IGBT elements 21 a is fed back to the AND circuit 10 inorder to control driving of the IGBT elements 21 a. Specifically,driving the IGBT elements 21 a according to the gate potential Vg isprovided with a hysteresis. When the IGBT elements 21 a have been turnedoff, a current readily flows into the diode elements 22 a. Therefore, bycomparing the potential difference Vs with the smaller second diodecurrent sensing threshold H2, the IGBT elements 21 a can be turned offat the timing at which a current flows into the diode elements 22 a.

Moreover, when the IGBT elements 21 a have been turned on, a currentdoes not readily flow into the diode elements 22 a. Therefore, bycomparing the potential difference Vs with the larger first diodecurrent sensing threshold H1, as long as no current flows into the diodeelements 22 a, the IGBT elements 21 a can be turned on.

Consequently, the interference between the action of the diode elements22 a and the action of the IGBT elements 21 a can be avoided in order toprevent an increase in a forward loss in the diode part 22. In addition,the IGBT elements 21 a can be controlled stably without being caused tochatter or vibrate.

Incidentally, the first feedback circuit 41 is equivalent to the firstfeedback means or the first feedback unit, and the AND circuit 10 andsecond feedback circuit 42 are equivalent to the second feedback meansor the second feedback unit.

Tenth Embodiment

In the ninth embodiment, an output of the AND circuit 10 (gate potentialVg) is inputted to the first feedback circuit 41 in order to decide theon or off state of the IGBT elements 21 a. In the present embodiment, acircuit providing a hysteresis is employed. Thus, the same actions asthose in the semiconductor device of the ninth embodiment are performedwithout the necessity of sensing the gate potential Vg.

FIG. 17 is a circuit diagram of a semiconductor device in accordancewith the present embodiment. As shown in the drawing, the potentialdifference Vs in the sense resistor 30 is inputted to an IGBT feedbackcircuit 43 and a diode Schmitt circuit 44. Moreover, an external PWMgate signal and the output of the IGBT feedback circuit 43 are inputtedto an AND circuit 11, and the external PWM gate signal and the output ofthe diode Schmitt circuit 44 are inputted to an AND circuit 12. Further,the outputs of the AND circuits 11 and 12 are inputted to an OR circuit13, and the output of the OR circuit 13 is inputted as the gatepotential Vg to the IGBT elements 21 a.

The IGBT feedback circuit 43 detects an over current flowing into theIGBT elements 21 a and has an over current sensing threshold Vth2. TheIGBT feedback circuit 43 inputs the potential difference Vs between theterminals of the sense resistor 30 and compares the potential differenceVs with the over current sensing threshold Vth2. As shown in FIG. 18A,if the potential difference Vs exceeds the over current sensingthreshold Vth2, the IGBT feedback circuit 43 outputs a signal with whichthe IGBT elements 21 a are turned off.

Moreover, the diode Schmitt circuit 44 senses a current flowing into thediode elements 22 a, and has the thresholds H1 and H2 employed in theninth embodiment. The diode Schmitt circuit 44 inputs the potentialdifference Vs between the terminals of the sense resistor 30 andcompares the potential difference with the threshold H1 or H2. As shownin FIG. 18B, when the potential difference Vs increases from a negativeside to a positive side, if the potential difference Vs exceeds thesecond diode current sensing threshold H2, the diode Schmitt circuit 44outputs a signal with which the IGBT elements 21 a are turned on.

When the potential difference Vs decreases from the positive side to thenegative side, if the potential difference Vs falls below the firstdiode current sensing threshold H1, the diode Schmitt circuit 44 outputsa signal with which the IGBT elements 21 a are turned off.

When both the PWM gate signal and the output of the IGBT feedbackcircuit 43 have a high level, the AND circuit 11 outputs a high-levelsignal. On the other hand, when both the PWM gate signal and the outputof the diode Schmitt circuit 44 have the high level, the AND circuit 12outputs the high-level signal.

When the OR circuit 13 inputs the high-level signal from either of theAND circuits 11 and 12, the OR circuit 13 outputs a signal with whichthe IGBT elements 21 a are turned on so that the IGBT elements 21 a willbe turned on. On the other hand, when the high-level signal is notinputted from the AND circuits 11 and 12, the OR circuit 13 does notoutput the signal with which the IGBT elements 21 a are turned on. TheIGBT elements 21 a are therefore turned off.

As mentioned above, the IGBT feedback circuit 43 intended to implementfeedback control by sensing an over current in the IGBT elements 21 aand the diode Schmitt circuit 44 intended to implement feedback controlby sensing a diode current are included independently of each other. Theoutputs of the circuits 43 and 44 are synthesized with the PWM gatesignal and then synthesized by the OR circuit 13. Consequently,similarly to the ninth embodiment, driving of the IGBT elements 21 a canbe controlled to exhibit a hysteresis.

Incidentally, the IGBT feedback circuit 43, AND circuit 11, and ORcircuit 13 are equivalent to the IGBT feedback means or the UGBTfeedback unit, and the diode Schmitt circuit 44, AND circuit 12, and ORcircuit 13 are equivalent to the diode Schmitt means or the diodeSchmitt unit.

Eleventh Embodiment

In the present embodiment, a sense resistor dedicated to the IGBTsensing elements 21 b and a sense resistor dedicated to the diodesensing elements 22 b are included.

FIG. 19 is a circuit diagram of a semiconductor device in accordancewith the present embodiment. As shown in the drawing, a first senseresistor 31 is connected to the IGBT sensing elements 21 b, and thefirst potential difference Vs1 between the terminals of the first senseresistor 31 is inputted to the IGBT sensing Schmitt circuit 45.Moreover, a second sense resistor 32 is connected to the diode sensingelements 22 b, and the second potential difference Vs2 between theterminals of the second sense resistor 32 is inputted to the diodesensing Schmitt circuit 46.

The IGBT sensing Schmitt circuit 45 detects an over current flowing intothe IGBT elements 21 a, and has a first over current sensing thresholdVth2 and a second over current sensing threshold Vth2′, which is smallerthan the first over current sensing threshold Vth2, for the firstpotential difference Vs1. The IGBT sensing Schmitt circuit 45 inputs thefirst potential difference Vs1 between the terminals of the first senseresistor 31 and compares the first potential difference Vs1 with thethreshold Vth2 or Vth2′. As indicated in FIG. 20A, when the firstpotential difference Vs1 increases from a negative side to a positiveside, if the first potential difference Vs1 exceeds the first overcurrent sensing threshold Vth2, the IGBT sensing Schmitt circuit 45outputs a signal with which the IGBT elements 21 a are turned off. Whenthe first potential difference Vs1 decreases from the positive side tothe negative side, if the first potential difference Vs1 falls below thesecond over current sensing threshold Vth2′, the IGBT sensing Schmittcircuit 45 outputs a signal with which the IGBT elements 21 a are turnedon.

The diode sensing Schmitt circuit 46 is identical to the diode Schmittcircuit 44 employed in the tenth embodiment. Consequently, as indicatedin FIG. 20B, when the second potential difference Vs2 increases from thenegative side to the positive side, if the second potential differenceVs2 exceeds the second diode current sensing threshold H2, the diodesensing Schmitt circuit 46 outputs a signal with which the IGBT elements21 a are turned on. When the second potential difference Vs2 decreasesfrom the positive side to the negative side, if the second potentialdifference Vs2 falls below the first diode current sensing threshold H1,the diode sensing Schmitt circuit 46 outputs a signal with which theIGBT elements 21 a are turned off.

Similarly to the tenth embodiment, when the AND circuits 11 and 12 andOR circuit 13 are put into action, the IGBT elements 21 a are driven.

As mentioned above, since the sense resistors 31 and 32 are included inassociation with the IGBT sensing elements 21 b and diode sensingelements 22 b, the thresholds H1, H2, Vth2, and Vth2′ can be set tooptimal values according to the output characteristics of the IGBTsensing elements 21 b and diode sensing elements 22 b. The freedom indesigning can be improved.

Incidentally, IGBT sensing Schmitt circuit 45, AND circuit 11, and ORcircuit 13 are equivalent to the IGBT sensing Schmitt means or the IGBTsensing Schmitt unit, and the diode sensing Schmitt circuit 46, ANDcircuit 12, and OR circuit 13 are equivalent to the diode sensingSchmitt means or the diode sensing Schmitt unit.

Twelfth Embodiment

In the present embodiment, a semiconductor device shown in FIG. 19 andprovided with the temperature sensitive diode elements 50 shown in FIG.3 is integrated into a semiconductor chip 60.

FIG. 21 is a plan view of the semiconductor chip 60 in accordance withthe present embodiment. As shown in FIG. 21, the semiconductor chip 60includes an IGBT 21 a with a body diode, temperature sensitive diodeelements 50, a processing circuit unit 71, current sensing elements 61,a gate pad 62, a guard ring 63, an emitter pad 64, and a power supplypad 65.

The processing circuit unit 71 is a circuit unit into which the IGBTfeedback circuit 43, diode Schmitt circuit 44, sense resistor 30, ANDcircuits 11 and 12, and OR circuit 13 which are shown in FIG. 17 areintegrated.

The emitter pad 64 is an electrode connected to a load. The power supplypad 65 is an electrode through which a voltage is applied from a powersupply to the IGBT feedback circuit 43 and diode Schmitt circuit 44.Assuming that the surface of the semiconductor chip 60 shown in FIG. 21is the face thereof, a collector pad is disposed in the back of thesemiconductor chip 60.

As mentioned above, the semiconductor device can be fabricated into achip as the semiconductor chip 60. Consequently, the general-purposeproperty can be improved.

Other Embodiments

In the aforesaid embodiments, the IGBT part 21 is controlled accordingto a pulse width modulation (PWM) control method. However, the PWMcontrol is a mere form of control. The IGBT elements 21 a may be drivenin, for example, a full-on mode.

In the aforesaid embodiments, the feedback circuit 40 decides both acurrent flowing into the diode elements 22 a and an over current flowinginto the IGBT elements 21 a. A semiconductor device may be designed sothat the feedback circuit 40 decides only the current flowing into thediode part 22. In this case, the IGBT part 21 need not include the IGBTsensing elements 21 b. The semiconductor device may include as the IGBT20 with a body diode the IGBT elements 21 a and the diode part 22.Moreover, Hall-effect elements may be adopted as elements that detectcurrent components flowing into the respective diode elements 21 a. Thesame applies to the first feedback circuit 41, second feedback circuit42, IGBT feedback circuit 43, diode Schmitt circuit 44, IGBT sensingSchmitt circuit 45, and diode sensing Schmitt circuit 46.

In the aforesaid embodiments, the diode current sensing thresholds Vth1and Vth1′ and thresholds H1 and H2 are set to negative values, and theover current sensing thresholds Vth2 and Vth2′ are set to positivevalues. This is a mere example of threshold values. The presentinvention is not limited to the threshold values. Moreover, the diodecurrent sensing thresholds Vth1 and Vth1′, thresholds H1 and H2, andover current sensing thresholds Vth2 and Vth2′ are set to voltagevalues. However, when the feedback means or the feedback unit includingthe AND circuit 10, sense resistor 30, and feedback circuit 40 detects acurrent flowing into the diode elements 22 a, the threshold values arecurrent values.

The temperature sensitive diode elements 50 employed in the secondembodiment may be included in the semiconductor devices of the ninth toeleventh embodiments. In this case, as shown in FIG. 4, the thresholdsH1 and H2 are changed to thresholds H1′ and H2′ larger than thethresholds H1 and H2. The potential difference Vs or Vs2 is comparedwith the threshold H1′ or H2′.

Thirteenth Embodiment

FIG. 22 is a plan view showing the outline construction of asemiconductor device in accordance with the thirteenth embodiment. FIG.23 is a sectional view along an XXIII-XIII cutting-plane line shown inFIG. 22. The semiconductor device of the present embodiment is used as apower switching device in, for example, an inverter module for electricand hybrid vehicles (EHVs).

As shown in FIG. 22 and FIG. 23, the semiconductor device 701 includes asemiconductor substrate 710 of a first conductivity type. Thesemiconductor substrate 710 has a main region 730 and a sense region 750whose principal surfaces are smaller than those of the main region 730.In the main region 730, insulated-gate bipolar transistor (IGBT)elements 731 each having a commutation diode element 732 (that is, afreewheeling diode (FWD) element 732) incorporated therein (so-calledreverse-conducting (RC) IGBT elements) are formed. Moreover, in thesense region 750, IGBT-only sensing elements 751 and FWD element-onlysensing elements 752 are formed. The semiconductor device 701 of thepresent embodiment is characterized in that the FWD element-only sensingelements 752 are disposed in the semiconductor substrate 710 in whichthe RC-IGBT elements are formed. As the other components, knownstructures can be adopted. To begin with, the main region 730 will bedescribed below.

In the present embodiment, as the semiconductor substrate 710, amonocrystalline bulk silicon substrate of n-type conductivity (n−) (FZwafer) whose impurity density is, for example, on the order of 1×10¹⁴cm⁻³ is adopted. The part of the main region 730 of the semiconductorsubstrate 710 functions as the drift layers of the IGBT elements 731 andthe cathodes of the FWD elements 732 (pn-junction diodes). Base regions711 of p-type conductivity (p) are selectively formed in the superficiallayer of the first principal surface of the semiconductor substrate 710within the main region 730.

The base regions 711 are used as regions to be formed as channels of theIGBT elements 731 and the anode regions of the FWD elements 732. In thebase regions 711, trenches which penetrate through the base regions 711from the first principal surface of the semiconductor substrate 710 andwhose bottoms reach the semiconductor substrate 710 are selectivelyformed. A polysilicon whose impurity density is on the order of 1×10²⁰cm⁻³ is poured into the trenches through gate insulating films (notshown) formed on the bottoms and flanks of the trenches, whereby gateelectrodes 712 are formed.

Moreover, in the base regions 711, emitter regions 713 of n-typeconductivity (n+) are selectively formed in the superficial layer of thefirst principal surface adjacently to the flanks of the gate electrodes712 (trenches). In the present embodiment, the emitter regions 713 havea thickness of about 0.5 μm and have an impurity density of about 1×10¹⁹cm⁻³. The emitter regions 713 are electrically connected to emitterelectrodes (not shown) made of, for example, an aluminum material.

Moreover, each of the emitter regions 713 is formed in only one ofadjoining base regions 711 out of the multiple base regions segmented bythe gate electrodes 712 (trenches). Consequently, the base regions 711are classified into multiple first regions 711 a each of which includesthe emitter region 713 and is electrically connected to the emitterelectrode, and multiple second regions 711 b each of which does notinclude the emitter region 713. In other words, the first regions 711 aand second regions 711 b are alternately arranged. Among the multiplesecond regions 711 b, at least part of the second regions 711 b iselectrically connected to the emitter electrodes. Among the base regions711, in the regions electrically connected to the emitter electrodes(all of the first regions 711 a and at least part of the second regions711 b), contact regions (not shown) of p-type conductivity (p+) having athickness of about 0.8 μm and an impurity density of about 1×10¹⁹ cm⁻³are selectively formed in the superficial layer of the first principalsurface.

In the superficial layer of the second principal surface of thesemiconductor substrate 710 within the main region 730, collector layers714 of p-type conductivity (p+) are selectively formed. In the presentembodiment, the collector layers 714 have a thickness of about 0.5 μmand an impurity density of about 1×10¹⁸ cm⁻³. The collector layers 714and cathode layers 715 are electrically connected to collectorelectrodes (not shown) made of, for example, an aluminum material.

In the present embodiment, as shown in FIG. 23, a field stop layer 716of n-type conductivity (n) is formed between the semiconductor substrate710 and the collector layers 714 and cathode layers 715. When IGBTelements sharing the field stop layer 716 that terminates depletionlayers are adopted as IGBT elements each having the trench gatestructure, compared with when IGBT elements having any other trenchstructure (of a punch-through type or a non-punch-through type) areadopted, the thickness of the semiconductor substrate 710 (semiconductordevice 701) can be reduced. Consequently, since the number of excessivecarriers is small, and the remaining width of a neutral region with eachof the depletion layers is fully stretched is limited, a switching losscan be minimized. Incidentally, the thickness from the surfaces of thebase regions 711 shown in FIG. 23 (the first principal surface of thesemiconductor substrate 710) to the surfaces of the collector layers 714(the second principal surface of the semiconductor substrate 710) isabout 130 μm.

As mentioned above, in the main region 730 of the semiconductorsubstrate 710, the IGBT elements 731 and FWD elements 732 are integratedwith each other. Specifically, the anode electrodes of the FWD elements732 and the emitter electrodes of the IGBT elements 731 are formed incommon, and the cathode electrodes of the FWD elements 732 and thecollector electrodes of the IGBT elements 731 are formed in common.Next, the sense region 750 will be described below.

As a region of the semiconductor substrate 710 other than the regionformed as the main region 730, the sense region 750 is formed over arange whose principal surfaces are smaller than those of the main region730. In the sense region 750, the IGBT-only sensing elements 751 whichhave the same structure as the IGBT elements 731 do and into which acurrent proportional to a current flowing into the IGBT elements 731flows are formed. Moreover, the FWD-only sensing elements 752 which havethe same structure as the FWD elements 732 do and into which a currentproportional to a current flowing into the FWD elements 732 flows areformed in the sense region. Specifically, the area of the IGBT-onlysensing elements 751 is about one-thousandths of the area of the IGBTelements 731, and the area of the FWD-only sensing elements 752 is aboutone-thousandths of the area of the FWD elements 732.

To be more specific, base regions 717 of p-type conductivity (p) areselectively formed in the superficial layer of the first principalsurface of the semiconductor substrate 710 within the sense region 750.The base regions 717 are used as regions formed as the channels of theIGBT-only sensing elements 751. Trenches which penetrate through thebase regions 717 from the first principal surface of the semiconductorsubstrate 710 and whose bottoms reach the semiconductor substrate 710are selectively formed in the base regions 717. A polysilicon whoseimpurity density is, for example, on the order of 1×10²⁰ cm⁻³ is pouredinto the trenches through gate insulating films (not shown) formed onthe bottoms and flanks of the trenches, whereby gate electrodes 718 areformed.

Moreover, in the base regions 717, emitter regions 719 of n-typeconductivity (n+) are selectively formed in the superficial layer of thefirst principal surface adjacently to the flanks of the gate electrodes718 (trenches). In the present embodiment, the emitter regions 719 havea thickness of about 0.5 μm and an impurity density of about 1×10¹⁹cm⁻³. The emitter regions 719 are electrically connected to emitterelectrodes (not shown) made of, for example, an aluminum material.

Moreover, anode regions 720 of p-type conductivity (p) are selectivelyformed separately from the base regions 717 in the superficial layer ofthe first principal surface of the semiconductor substrate 710 withinthe sense region 750. The anode regions 720 function as the anodes ofthe FWD-only sensing elements 752. In the anode regions 720, contactregions (not shown) of p-type conductivity (p+) are selectively formedto have a thickness of about 0.8 μm and an impurity density of about1×10¹⁹ cm⁻³.

Collector layers 721 of p-type conductivity (p+) are selectively formedin the superficial layer of the second principal surface of thesemiconductor substrate 710 within the sense region 750 so that thecollector layers will include the regions immediately below the baseregions 717. In the present embodiment, the collector layers 721 have athickness of about 0.5 μm and an impurity density of about 1×10¹⁸ cm⁻³.Moreover, cathode layers 722 of n-type conductivity (n+) are selectivelyformed over a range in the superficial layer of the second principalsurface of the semiconductor substrate 710 other than a range thereof,over which the collector layers 721 are formed, immediately below theanode regions 720. In the present embodiment, the cathode layers 722have a thickness of about 0.5 μm and an impurity density of about 1×10¹⁸cm⁻³. The collector layers 721 and cathode layers 722 are electricallyconnected to the collector electrodes (not shown) in common with thecollector layers 714 and cathode layers 715 within the main region 730.

As mentioned above, in the present embodiment, the IGBT-only sensingelements 751 and FWD-only sensing elements 752 are formed independentlyof each other within the sense region 750 of the semiconductor substrate710.

Preferably, the cathode layers 722 are formed separately from the baseregions 711 of the IGBT elements 731 and the base regions of theIGBT-only sensing elements 751 in a direction perpendicular to thethickness direction of the semiconductor substrate 710. In the presentembodiment, the FWD-only sensing elements 752 are formed so that thelengths from the base regions 711 of the IGBT elements 731 within themain region 730 to the cathode layers 722 will be equal to or largerthan the thickness of the semiconductor substrate 710. Moreover, theFWD-only sensing elements 752 are formed so that the length D1 from thebase regions 717 to the cathode layers 722 in the directionperpendicular to the thickness direction of the semiconductor substrate710 will be equal to or larger than the thickness of the semiconductorsubstrate 710. Well regions 723 of p-type conductivity (p) are formedbetween the base regions 717 and anode regions 720 in the superficiallayer of the first principal surface of the semiconductor substrate 710for the purpose of improving a dielectric strength. Moreover, thecollector layers 721 are extended to immediately below the well regions723 and to the boundaries of the cathode layers 722 (the boundaries ofthe anode regions 720 in the direction perpendicular to the thicknessdirection of the semiconductor substrate 710).

As shown in FIG. 23, a guard ring 724 of p-type conductivity is formedas an electric-field concentration inhibitor in the superficial layer ofthe first principal surface in the marginal region of the semiconductorsubstrate 710 (near the margin thereof) so that the guard ring willsurround the main region 730 and sense region 750. Moreover, referencenumeral 790 in FIG. 22 denotes a gate pad through which a driving signalis applied to the gate electrodes 712, and reference numeral 791 denotesan emitter sensing pad. Reference numeral 792 denotes an IGBT sensingpad connected to the emitter regions 719 of the IGBT-only sensingelements 751, and reference numeral 793 denotes an FWD sensing padconnected to the anode regions 720 of the FWD-only sensing elements 752.

Next, a feedback circuit for a gate driving signal to which thesemiconductor device 701 having the foregoing construction is adaptedwill be described below.

FIG. 24 shows an example of the feedback circuit to which thesemiconductor device of the present embodiment is adapted. FIG. 25 showsthe relationship among the potential difference Vs between the terminalsof a sense resistor, a diode current sensing threshold Vth1, an overcurrent sensing threshold Vth2, and an output of a feedback unit. Thefeedback circuit is formed as part of an inverter circuit (one of upperand lower arms), and is identical to that (semiconductor device)described in JP-A-2007-229959 filed by the present inventor. In relationto the present embodiment, the description of the feedback circuit willbe omitted. FIG. 24 shows an example in which the sense resistor isshared by the IGBT-only sensing elements 751 and FWD-only sensingelements 752.

As shown in FIG. 24, the feedback circuit includes the aforesaidsemiconductor device 701, an AND circuit 810, a sense resistor 811, anda feedback unit 812.

The AND circuit 810 is a logic circuit that when all inputted signalshave a high level, outputs a high-level signal. An externalpulse-width-modulated (PWM) gate signal (equivalent to a driving signal)with which the semiconductor device 701 (IGBT elements 731 and IGBT-onlysensing elements 751) is driven, and an output of the feedback unit 812are inputted to the AND circuit 810. The PWM gate signal is produced byan external PWM signal generation circuit or the like, and applied tothe input terminal of the AND circuit 810.

The AND circuit 810 is electrically connected to the gate pad 790 of thesemiconductor device 701 via a gate resistor 813. The gate voltages ofthe IGBT elements 731 and IGBT-only sensing elements 751 are controlledwith the PWM gate signal fed from the AND circuit 810 via the gateresistor 813. For example, if the PWM gate signal whose passage throughthe AND circuit 810 is permitted is a high-level signal, the IGBTelements 731 are turned on in order to drive the IGBT elements. If thePWM gate signal is a low-level signal, the IGBT elements 731 are turnedoff in order to cease driving the IGBT elements. Moreover, if thepassage of the PWM gate signal through the AND circuit 810 is ceased,the IGBT elements 731 and IGBT-only sensing elements 751 are not driven.

Moreover, a load, a power supply, or the like that is not shown isconnected to the collectors of the IGBT elements 731 so that a maincurrent will flow between the collectors of the IGBT elements 731 andthe emitters thereof. Moreover, the collectors of the IGBT-only sensingelements 751 are formed in common with the collectors of the IGBTelements 731. The emitter regions 719 of the IGBT-only sensing elements751 are connected to one of the terminals of the sense resistor 811 viathe pad 792 for the IGBT-only sensing elements 751. The other terminalof the sense resistor 811 is connected to the emitter regions 713 of theIGBT elements 731 via the emitter sensing pad 791. Consequently, a sensecurrent for current detection flowing from the emitter regions 719 ofthe IGBT-only sensing elements 751, that is, a current proportional to amain current flowing into the IGBT elements 731 flows into the senseresistor 811. The potential difference Vs between the terminals of thesense resistor 811 is fed back to the feedback unit 812.

The feedback unit 812 is formed with a combination of, for example,operational amplifiers or the like, decides whether a current has flowedinto the FWD elements 732 or whether an over current has flowed into theIGBT elements 731, and permits or ceases the passage of the PWM gatesignal, which is inputted to the AND circuit 810, on the basis of theresult of the decision. Therefore, the feedback unit 812 has a diodecurrent sensing threshold Vth1 to be used to decide whether a currenthas flowed into the FWD elements 732, and an over current sensingthreshold Vth2 to be used to decide whether an over current has flowedinto the IGBT elements 731. In the present embodiment, the thresholdsVth1 and Vth2 are set to voltage values.

If the IGBT elements 731 are normally driven (if no current flows intothe FWD elements 732), a current flows from the IGBT-only sensingelements 751 to the sense resistor 811. Consequently, assuming that thepotential at the emitter regions 713 of the IGBT elements 731 isregarded as a reference, the potential difference Vs between theterminals of the sense resistor 811 has a positive value. In contrast,if a current flows into the FWD elements 732, a current flows from thesense resistor 811 to the FWD-only sensing elements 752. Consequently,assuming that the potential at the emitter regions 713 of the IGBTelements 732 is regarded as a reference, the potential difference Vsbetween the terminals of the sense resistor 811 has a negative value.Therefore, the diode current sensing threshold Vth1 for use in detectingwhether a current has flowed into the FWD elements 732 is set to anegative value. Moreover, if an over current flows into the IGBTelements 731, the value of a sense current flowing from the IGBT-onlysensing elements 751 to the sense resistor 811 gets larger, that is, thepotential difference Vs between the terminals of the sense resistor 811has a larger positive value. Therefore, the over current sensingthreshold Vth2 is set to a positive value.

For driving the IGBT elements 731, the feedback unit 812 outputs asignal with which the passage of the PWM gate signal to be inputted tothe AND circuit is permitted, and inputs the potential difference Vsbetween the terminals of the sense resistor 811. As shown in FIG. 25,when the potential difference Vs is smaller than the diode currentsensing threshold Vth1, or when the potential difference Vs is largerthan the over current sensing threshold Vth2, the feedback unit 812outputs a signal with which the passage of the PWM gate signal to beinputted to the AND circuit 810 is ceased.

For example, normally, the PWM gate signal is produced as a drivingsignal, with which the IGBT elements 731 (and the IGBT-only sensingelements 751) are driven, by an external circuit such as a PWM signalgeneration circuit, and inputted to the AND circuit 810. On the otherhand, the FWD elements 732 are turned off, and no current flows intoeven the FWD-only sensing elements 752. Consequently, the potential atone of the terminals of the sense resistor 810, which is connected tothe emitter regions 719 of the IGBT-only sensing elements 751 (IGBTsensing pad 792) gets higher than the potential at the other terminalthereof. Eventually, the potential difference Vs between the terminalsof the sense resistor 811 has a positive value.

Consequently, as shown in FIG. 25, the potential difference Vs is largerthan the negative diode current sensing threshold Vth1, the feedbackunit 812 decides that no current has flowed into the FWD elements 732.Therefore, the output of the feedback unit 812 is, as shown in FIG. 25,brought to a high level, and inputted to the AND circuit 810. When thehigh-level PWM gate signal and the high-level output of the feedbackunit 812 are inputted to the AND circuit 810, the PWM gate signal hasthe passage thereof through the AND circuit 810 permitted, and isinputted to the gate electrodes 712 and 718 of the IGBT elements 731 andIGBT-only sensing elements 751 via the gate resistor 813. The IGBTelements 731 and IGBT-only sensing elements 751 are turned on.Consequently, the IGBT elements 731 and IGBT-only sensing elements 751are driven, and a current flows into the load that is not shown and thatis connected to the collector electrodes or emitter electrodes of theIGBT elements 731.

When a current flows into the FWD elements 732, the potential at one ofthe terminals connected to the anodes 711 (emitter sensing pad 791) ofthe FWD elements 732 gets higher than the potential at the otherterminal thereof connected to the anode regions 720 (FWD sensing pad793) of the FWD-only sensing elements 752. Consequently, the potentialdifference between the terminals of the sense resistor 811 becomesnegative.

Consequently, as shown in FIG. 25, when the potential difference Vs getssmaller than the diode current sensing threshold Vth1, the feedback unit812 decides that current has flowed into the FWD elements 732.Therefore, the output of the feedback unit 812 is an output with whichthe passage of the PWM gate signal, which is inputted to the AND circuit810, is ceased, and is then inputted to the AND circuit 810.

Consequently, since a signal with which the IGBT elements 731 are drivenis not inputted from the AND circuit 810, driving the IGBT elements 731is ceased (the gate signal is set to a zero level). Namely, when the FWDelements 732 act in the forward direction, the IGBT elements 731 are notput into action.

Moreover, if an over current flows into the IGBT elements 731, a sensecurrent flowing from the IGBT-only sensing elements 751 to the senseresistor 811 gets larger proportionally to the over current.Consequently, the potential difference Vs between the terminals of thesense resistor 811 gets larger than the potential difference Vs attainedwhen the IGBT elements 731 act normally.

Consequently, as shown in FIG. 25, when the potential difference Vs getslarger than the over current sensing threshold Vth2, the feedback unit812 decides that an over current has flowed into the IGBT elements 731.Therefore, the output of the feedback unit 812 is an output with whichthe passage of the PWM gate signal to be inputted to the AND circuit 810is ceased, and is then inputted to the AND circuit 810.

Consequently, since a signal with which the IGBT elements 731 are drivenis not inputted from the AND circuit 810, driving the IGBT elements 731is ceased. In other words, the IGBT elements 731 are protected frombeing broken with an over current flowing into the IGBT elements 731.

As described so far, in the semiconductor device 701 of the presentembodiment, the FWD-only sensing elements 752 are disposed within thesense region 750 of the semiconductor substrate 710 in such a mannerthat they are devoid of a gate electrode to which the PWM gate signal isapplied. When the FWD-only sensing elements 752 act in the forwarddirection, the anode regions 720 of the FWD-only sensing elements 752and the cathode regions (semiconductor substrate 710) thereof will notbe brought to the same potential. Therefore, the FWD-only sensingelements 752 will not be able to readily act in the forward directiondue to the gate potential thereof (PWM gate signal). In other words, acurrent proportional to a current flowing into the FWD elements 732readily flows into the FWD-only sensing elements 752 (a detectivevoltage is readily developed). Consequently, when the semiconductordevice 701 having the FWD-only sensing elements 752 is adapted, whetherthe PWM gate signal has been applied to the gate electrodes 712 of theIGBT elements 731 can be highly precisely controlled based on the actionof the FWD elements 732. In other words, although the FWD elements 732are incorporated in the IGBT elements 731, an increase in a forward losscaused by the FWD elements 732 can be effectively suppressed.

Moreover, in the present embodiment, the cathode layers 722 included inthe FWD-only sensing elements 752 are disposed within the sense region750 of the semiconductor substrate 710, and are formed separately fromthe base regions 711 of the IGBT elements 731 disposed in the mainregion 730 in the direction perpendicular to the thickness direction ofthe semiconductor substrate 710. Moreover, the cathode layers 722 areformed separately from the base regions 717 of the IGBT-only sensingelements 751 in the direction perpendicular to the thickness directionof the semiconductor substrate 710. Consequently, the FWD-only sensingelements 751 are prevented from incorrectly acting because at least partof carriers accumulated in the semiconductor substrate 710 along withthe action of the IGBT elements 731 (the action of the IGBT-only sensingelements 751) (holes injected from the collector layers 714 and 721included in the IGBT elements 731 and IGBT-only sensing elements 751)flows into the cathode layers 722 of the FWD-only sensing elements 752.In other words, current detection to be performed using the FWD-onlysensing elements 752 can be more accurately achieved according to theaction of the FWD elements 732 (a current flowing into the FWD elements732).

In the present embodiment, the distance between the base regions 711 and717 and the cathode layers 722 in the direction perpendicular to thethickness direction of the semiconductor substrate 710 is equal to orlarger than the thickness of the semiconductor substrate 710.Consequently, holes injected from the collector layers 714 and 721included in the IGBT elements 731 and IGBT-only sensing elements 751readily flow into the channels and the emitter regions 713 and 719 buthardly flow into the cathode layers 722. Therefore, the precision incurrent detection by the FWD-only sensing elements 752 can be upgraded.

In the present embodiment, the cathode layers 722 of the FWD-onlysensing elements 752 are formed immediately below the anode regions 720.Namely, the distance between the anode regions 720 and cathode layers722 is the shortest. Consequently, the action resistance offered by theFWD-only sensing elements 752 can be reduced, a current can readily flow(a detective voltage can be readily developed), and the precision incurrent detection by the FWD-only sensing elements 752 can be upgraded.

Fourteenth Embodiment

Next, the fourteenth embodiment of the present invention will bedescribed in conjunction with FIG. 26. FIG. 26 is a sectional viewshowing the outline construction of a semiconductor device in accordancewith the fourteenth embodiment, and is comparable to FIG. 23 showing thethirteenth embodiment.

The semiconductor device in accordance with the fourteenth embodimenthas a lot in common with the thirteenth embodiment. The description ofthe common parts will be omitted, and a different part will beintensively described below. The same reference numerals will beassigned to the components identical to those of the thirteenthembodiment.

As shown in FIG. 26, in the present embodiment, the FWD-only sensingelements 752 include dummy gate electrodes 725 which are formed byputting a conducting material to trenches, which penetrate through theanode regions 720 from the first principal surface and whose bottomsreach the semiconductor substrate 710, through insulating films. Thedummy gate electrodes 725 have the same structure as the gate electrodes712 of the IGBT elements 731 formed in the main region 730, and aregrounded. The dummy gate electrodes 725 are therefore electricallyindependent of the gate electrodes 712. Moreover, dummy emitter regions726 of n-type conductivity (n+) are selectively formed in thesuperficial layer of the first principal surface adjacently to theflanks of the dummy gate electrodes 725 (trenches). Although the dummyemitter regions 726 have the same structure as the emitter regions 713of the IGBT elements 731 formed in the main region 730, the dummyemitter regions 726 are electrically independent of the emitter regions713.

As mentioned above, in the semiconductor device 701 of the presentembodiment, the dummy gate electrodes 725 that have the same structureas the gate electrodes 712 but are not electrically connected to thegate electrodes 712 and are grounded are included as parts of therespective FWD-only sensing elements 752. Consequently, although theFWD-only sensing elements 752 include the dummy gate electrodes 725having the same structure as the gate electrodes 712, when the FWD-onlysensing elements 752 act in the forward direction, the anode regions 720of the FWD-only sensing elements 752 and the cathode regions(semiconductor substrate 710) thereof will not be brought to the samepotential. The FWD-only sensing elements 752 will not be able to readilyact in the forward direction due to the gate potential (PWM gatesignal). In other words, a current proportional to a current flowinginto the FWD elements 732 readily flow into the FWD-only sensingelements 752 (a detective voltage is readily developed). Consequently,even when the semiconductor device 701 including the FWD-only sensingelements 752 is adapted, whether the PWM gate signal is applied to thegate electrodes 712 of the IGBT elements 731 can be highly preciselycontrolled based on the action of the FWD elements 732. Namely, althoughthe FWD elements 732 are incorporated in the IGBT elements 731, anincrease in the forward loss caused by the FWD elements 732 can beeffectively suppressed.

Moreover, in the present embodiment, the dummy gate electrodes 725 anddummy emitter regions 726 have the same structures as the gateelectrodes 712 and emitter regions 713 respectively. Consequently, adesign ensuring the dielectric strength of the FWD-only sensing elements752 can be attained in the same manner as that of the FWD elements 732disposed in the main region 730.

In the present embodiment, the FWD-only sensing elements 752 furtherinclude, unlike those of the thirteenth embodiment, the grounded dummygate electrodes 725 and the dummy emitter regions 726. However, forexample, as shown in FIG. 27, the FWD-only sensing elements 752 mayfurther include only the grounded dummy gate electrodes 725 (devoid ofthe dummy emitter regions 726).

FIG. 27 is a sectional view showing a variant.

Fifteenth Embodiment

Next, the fifteenth embodiment of the present invention will bedescribed in conjunction with FIG. 28. FIG. 28 is a sectional viewshowing the outline construction of a semiconductor device in accordancewith the fifteenth embodiment, and is comparable to FIG. 23 showing thethirteenth embodiment.

The semiconductor device in accordance with the fifteenth embodiment hasa lot in common with the aforesaid embodiments. The description of thecommon parts will be omitted, and a different part will be intensivelydescribed. The same reference numerals will be assigned to componentsidentical to those of the aforesaid embodiments.

In the aforesaid embodiments, in the sense region 750, the base regions717 included in the IGBT-only sensing elements 751 and the anode regions720 included in the FWD-only sensing elements 752 are separated fromeach other.

In contrast, in the semiconductor device 701 of the present embodiment,for example, as shown in FIG. 28, IGBT-only sensing elements 751 whichinclude: base regions 727 of a second conductivity type selectivelyformed in the superficial layer of the first principal surface of thesemiconductor substrate 710; gate electrodes 718 formed by putting aconducting material to trenches, which penetrate through the baseregions 727 from the first principal surface in the centers 727 a of thebase regions 727 and of which bottoms reach the semiconductor substrate710, through insulating films; emitter regions 719 selectively formed inthe superficial layer of the first principal surface within the baseregions 727; collector layers 721 selectively formed in the secondprincipal surface of the semiconductor substrate 710, and into which acurrent proportional to a current flowing into the IGBT elements 731flows are disposed within the sense region 750.

Moreover, the perimeters 727 of the base regions 727 outside the centers727 a in which the gate electrodes 718 are formed are used as the anoderegions of the FWD-only sensing elements 752 (equivalent to the anoderegions 720 included in the thirteenth embodiment). Preferably, thecathode layers 722 of the FWD-only sensing elements 752 are formedseparately at least from the base regions 727 in a directionperpendicular to the thickness direction of the semiconductor substrate710 by a distance equal to or larger than the thickness of thesemiconductor substrate 710.

As mentioned above, in the semiconductor device 701 of the presentembodiment, the centers 727 a of the base regions 727 substantiallyfunction as the base regions of the IGBT-only sensing elements 751, andthe perimeters 727 b thereof function as the anode regions of theFWD-only sensing elements 752. In short, the base regions of theIGBT-only sensing elements 751 and the anode regions of the FWD-onlysensing elements 752 are formed as united bodies. Moreover, the cathodelayers 722 are formed separately from the base regions 727.

Consequently, while the same operation and advantage as those of thesemiconductor devices 1 of the aforesaid embodiments are exerted, theconstitution can be made smaller than those of the semiconductor devices1 of the aforesaid embodiments in the direction perpendicular to thethickness direction of the semiconductor substrate 710.

In the present embodiment, the semiconductor device 701 includes thefield stop layer 716. However, IGBT elements of a punch-through type ora non-punch-through type may be adopted as the IGBT elements 731(IGBT-only sensing elements 751).

Moreover, in the present embodiment, the first conductivity type setforth in Claims refers to the n-type conductivity and the secondconductivity type refers to the p-type conductivity (the constructionincluding the IGBT elements 731 having n-type channels). Alternatively,the first conductivity type may refer to the p-type conductivity and thesecond conductivity type may refer to the n-type conductivity (theconstruction including the IGBT elements 731 having p-type channels).

In the present embodiment, when the present embodiment is adapted to thefeedback circuit, the IGBT-only sensing elements 751 and FWD-onlysensing elements 752 share the sense resistor 811 to which they areconnected through one of the terminals thereof. Alternatively, theIGBT-only sensing elements 751 and FWD-only sensing elements 752 may beassociated with different sense resistors.

In the present embodiment, the sense resistor 811 is connected to theemitters of the IGBT-only sensing elements 751 and the anodes of theFWD-only sensing elements 752. Alternatively, a sense resistor may beconnected to the collectors of the IGBT-only sensing elements 751, and asense resistor may be connected to the cathodes of the FWD-only sensingelements 752.

In the present embodiment, the semiconductor device 701 includes assensing elements the IGBT-only sensing elements 751 and FWD-only sensingelements 752. However, the semiconductor device 701 may include as thesensing elements at least the FWD-only sensing elements 752.

In the present embodiment, the FWD-only sensing elements 752 include thecathode layers 722. Alternatively, the cathode layers 715 of the FWDelements 732 formed in the main region 730 may be used as the cathodelayers of the FWD-only sensing elements 752 (the cathode layers areshared by the FWD elements and FWD-only sensing elements). Even in thisconstruction, the cathode layers (cathode layers 715) of the FWD-onlysensing elements 752 can be formed separately from the base regions 717(or base regions 727) of the IGBT-only sensing elements 751. Inparticular, like the construction of the semiconductor device 701 of thefifteenth embodiment, in the construction in which the base regions ofthe IGBT-only sensing regions 751 and the anode regions of the FWD-onlysensing elements 752 are formed as the united bodies of the base regions727, the cathode layers 715 of the FWD elements 732 are thought to beadopted as the cathode layers formed separately from the base regions727.

However, the cathode layers 715 adjoin the collector layers 714 includedin the IGBT elements 731. Therefore, preferably, the cathode layers 722of the FWD-only sensing elements 752 are formed separately from thecathode layers 715 of the FWD elements 732.

In the present embodiment, the IGBT sensing pad 792 connected to theemitter regions 719 of the IGBT-only sensing elements 751 and the FWDsensing pad 793 connected to the anode regions 720 of the FWD-onlysensing elements 752 are formed independently of each other.Alternatively, for example, as shown in FIG. 29, the IGBT sensing pad792 and FWD sensing pad 793 may be formed in common as one sensing pad794. FIG. 29 is a plan view showing another variant.

The above disclosure has the following aspects.

According to a first aspect of the present disclosure, a semiconductordevice includes: a semiconductor substrate; a diode-built-ininsulated-gate bipolar transistor having an insulated-gate bipolartransistor and a diode, which are disposed in the substrate, wherein theinsulated-gate bipolar transistor includes a gate, and is driven with adriving signal input into the gate; and a feedback unit for detectingcurrent passing through the diode. The driving signal is input from anexternal unit into the feedback unit. The feedback unit passes thedriving signal to the gate of the insulated-gate bipolar transistor whenthe feedback unit detects no current through the diode. The feedbackunit stops passing the driving signal to the gate of the insulated-gatebipolar transistor when the feedback unit detects the current throughthe diode.

Consequently, when a current flows into the diode elements, driving theIGBT elements can be ceased. Namely, when a current flows into the diodeelements, a gate signal for use in driving the IGBT elements is notinputted to the IGBT elements. Consequently, the interference of theaction of the diode elements with the action of the IGBT elements can beavoided.

Consequently, since the diode elements and IGBT elements aresimultaneously turned on, an increase in the forward voltage of thediode elements derived from the fact that the diode elements formed inthe same semiconductor substrate as the IGBT elements are cannot readilyact in a forward direction can be avoided. Eventually, an increase in aloss in the forward voltage of the diode elements can be prevented.

Alternatively, the feedback unit may include a sensing resistor fordetecting the current through the diode. The feedback unit provides afirst diode current threshold for determining whether the current flowsthrough the diode. The feedback unit compares a voltage between two endsof the sensing resistor with the first diode current threshold. Thefeedback unit passes the driving signal to the gate of theinsulated-gate bipolar transistor when the voltage between two ends ofthe sensing resistor is equal to or larger than the first diode currentthreshold, and the feedback unit stops passing the driving signal to thegate of the insulated-gate bipolar transistor when the voltage betweentwo ends of the sensing resistor is smaller than the first diode currentthreshold.

As mentioned above, the circuitry including the sense resistor for thepurpose of detecting whether a current has flowed into the diodeelements will do. In this case, the potential difference between theterminals of the sense resistor can be used to detect the currentflowing into the diode elements.

Further, the diode-built-in insulated-gate bipolar transistor mayfurther include a diode current sensing element. The diode currentsensing element passes current in proportion to the current of thediode, and the current passing through the diode current sensing elementflows through the sensing resistor.

Further, the semiconductor device may further include: a temperaturesensing diode element for outputting a forward voltage corresponding totemperature generated in the diode-built-in insulated-gate bipolartransistor. The feedback unit further provides a second diode currentthreshold, which is larger than the first diode current threshold. Thefeedback unit replaces the first diode current threshold with the seconddiode current threshold so that the feedback unit compares the voltagebetween two ends of the sensing resistor with the second diode currentthreshold when the forward voltage is larger than a predeterminedforward voltage. The predetermined forward voltage corresponds to thetemperature in the diode-built-in insulated-gate bipolar transistorequal to or higher than a predetermined temperature. The feedback unitpasses the driving signal to the gate of the insulated-gate bipolartransistor when the voltage between two ends of the sensing resistor isequal to or larger than the second diode current threshold in a casewhere the forward voltage is larger than a predetermined forwardvoltage, and the feedback unit stops passing the driving signal to thegate of the insulated-gate bipolar transistor when the voltage betweentwo ends of the sensing resistor is smaller than the second diodecurrent threshold in a case where the forward voltage is larger than apredetermined forward voltage.

Consequently, when the IGBT with a body diode enters a high-temperaturestate, even if a current flowing into the diode elements is microscopic,the flow of the current into the diode elements can be decided.Consequently, when the IGBT with a body diode enters thehigh-temperature state and a small current flows into the diodeelements, driving the IGBT elements can be ceased. Eventually, the IGBTwith a body diode can be protected from being broken due to hightemperature.

Further, the feedback unit may further detect current passing throughthe insulated-gate bipolar transistor. The feedback unit passes thedriving signal to the gate of the insulated-gate bipolar transistor whenthe feedback unit detects no over current through the insulated-gatebipolar transistor. The over current is equal to or larger than apredetermined current, and the feedback unit stops passing the drivingsignal to the gate of the insulated-gate bipolar transistor when thefeedback unit detects the over current through the insulated-gatebipolar transistor.

As mentioned above, even when an over current flows into the IGBTelements, driving the IGBT elements can be ceased. The IGBT elements cantherefore be protected from being broken.

Furthermore, the predetermined current may provide an over currentthreshold. The feedback unit compares the voltage between two ends ofthe sensing resistor with the over current threshold. The feedback unitpasses the driving signal to the gate of the insulated-gate bipolartransistor when the voltage between two ends of the sensing resistor isequal to or smaller than the over current threshold, and the feedbackunit stops passing the driving signal to the gate of the insulated-gatebipolar transistor when the voltage between two ends of the sensingresistor is larger than the over current threshold.

Similarly to the case of the diode elements, a current flowing into theIGBT elements can be detected by utilizing the potential differencebetween the terminals of the sense resistor.

Furthermore, the diode-built-in insulated-gate bipolar transistor mayfurther include a IGBT current sensing element. The IGBT current sensingelement passes current in proportion to the current of theinsulated-gate bipolar transistor, and the current passing through theIGBT current sensing element flows through the sensing resistor.

According to a second aspect of the present disclosure, a semiconductordevice includes: a semiconductor substrate; a diode-built-in doublediffused metal oxide semiconductor transistor having a double diffusedmetal oxide semiconductor transistor and a diode, which are disposed inthe substrate; wherein the double diffused metal oxide semiconductortransistor includes a gate, which is driven with a driving signal inputinto the gate; and a feedback unit for detecting current passing throughthe diode. The driving signal is input from an external unit into thefeedback unit. The feedback unit stops driving the double diffused metaloxide semiconductor transistor when the feedback unit detects no currentthrough the diode, and the feedback unit drives the double diffusedmetal oxide semiconductor transistor so that current having a directionequal to a forward direction of the forward current flows through thedouble diffused metal oxide semiconductor transistor when the feedbackunit detects a forward current through the diode.

Consequently, when a forward current flows into the diode elements, thecurrent passes through the DMOS elements. Consequently, an increase in adc loss equivalent to a forward voltage Vf occurring when the forwardcurrent flows into the diode elements can be prevented.

Alternatively, the feedback unit may include a sensing resistor fordetecting the current through the diode. The feedback unit provides afirst diode current threshold for determining whether the current flowsthrough the diode. The feedback unit compares a voltage between two endsof the sensing resistor with the first diode current threshold. Thefeedback unit stops driving the double diffused metal oxidesemiconductor transistor when the voltage between two ends of thesensing resistor is equal to or larger than the first diode currentthreshold, and the feedback unit drives the double diffused metal oxidesemiconductor transistor when the voltage between two ends of thesensing resistor is smaller than the first diode current threshold.

As mentioned above, the potential difference occurring between theterminals of the sense resistor may be used to sense the flow of acurrent into the diode elements.

Further, the diode-built-in double diffused metal oxide semiconductortransistor may further include a diode current sensing element. Thediode current sensing element passes current in proportion to thecurrent of the diode, and the current passing through the diode currentsensing element flows through the sensing resistor so that the voltagebetween two ends of the sensing resistor is generated.

Further, the semiconductor device may further include: a temperaturesensing diode element for outputting a forward voltage corresponding totemperature generated in the diode-built-in double diffused metal oxidesemiconductor transistor. The feedback unit further provides a seconddiode current threshold, which is larger than the first diode currentthreshold. The feedback unit replaces the first diode current thresholdwith the second diode current threshold so that the feedback unitcompares the voltage between two ends of the sensing resistor with thesecond diode current threshold when the forward voltage is larger than apredetermined forward voltage. The predetermined forward voltagecorresponds to the temperature in the diode-built-in double diffusedmetal oxide semiconductor transistor equal to or higher than apredetermined temperature. The feedback unit stops driving the doublediffused metal oxide semiconductor transistor when the voltage betweentwo ends of the sensing resistor is equal to or larger than the seconddiode current threshold in a case where the forward voltage is largerthan a predetermined forward voltage, and the feedback unit drives thedouble diffused metal oxide semiconductor transistor when the voltagebetween two ends of the sensing resistor is smaller than the seconddiode current threshold in a case where the forward voltage is largerthan a predetermined forward voltage.

Consequently, even when the DMOS with a body diode acts at hightemperature at which a dc loss caused by the diode elements brings abouta trouble, a current flowing into the diode elements can be readilysensed. Consequently, even when a small current flows into the diodeelements, the DMOS elements can be turned on so that a current will flowinto the DMOS elements. Therefore, while an increase in the dc losscaused by the diode elements is prevented, heat dissipation of the diodeelements can be suppressed.

Further, the feedback unit may further provide a third diode currentthreshold, which is larger than the first diode current threshold. Thefeedback unit compares the voltage between two ends of the sensingresistor with the first diode current threshold so that the feedbackunit determines whether the feedback unit drives the double diffusedmetal oxide semiconductor transistor when the voltage between two endsof the sensing resistor decreases, and the feedback unit compares thevoltage between two ends of the sensing resistor with the third diodecurrent threshold so that the feedback unit determines whether thefeedback unit drives the double diffused metal oxide semiconductortransistor when the voltage between two ends of the sensing resistorincreases.

Consequently, even when the potential difference fluctuates due to noisein the vicinity of the first diode current sensing threshold or thirddiode current sensing threshold, the on and off states of the DMOSelements will not be switched due to the noise. Consequently, the noiseresistivity of the semiconductor device can be improved.

Further, the semiconductor device may further include: a driving unit.The feedback unit inputs the driving signal to the gate of the doublediffused metal oxide semiconductor transistor. The double diffused metaloxide semiconductor transistor is further driven with a switching signalinput into the gate from an external unit, and the driving unit drivesthe double diffused metal oxide semiconductor transistor according tothe switching signal so that the double diffused metal oxidesemiconductor transistor provides a switching element when the switchingsignal is input in the gate and the driving signal is not input in thegate.

Consequently, a semiconductor device having both a rectifying facilityrealized with the diode elements and a switching facility realized withthe DMOS elements can be provided.

According to a third aspect of the present disclosure, a semiconductordevice includes: a semiconductor substrate; a diode-built-ininsulated-gate bipolar transistor having an insulated-gate bipolartransistor and a diode unit, which are disposed in the substrate,wherein the insulated-gate bipolar transistor includes a gate, and isdriven with a driving signal input into the gate, wherein the diode unitincludes a diode element and a diode current sensing element, andwherein the diode current sensing element passes current in proportionto current flowing through the diode element; a sensing resistor coupledwith the diode current sensing element; and a feedback unit. The drivingsignal is input from an external unit into the feedback unit. Thefeedback unit provides a first diode current threshold, which defineswhether the diode element passes current. The feedback unit compares avoltage between two ends of the sensing resistor with the first diodecurrent threshold. The feedback unit passes the driving signal to thegate of the insulated-gate bipolar transistor so that the insulated-gatebipolar transistor turns on when the voltage between two ends of thesensing resistor is equal to or larger than the first diode currentthreshold, and the feedback unit stops passing the driving signal to thegate of the insulated-gate bipolar transistor so that the insulated-gatebipolar transistor turns off when the voltage between two ends of thesensing resistor is smaller than the first diode current threshold.

Consequently, when a current has flowed into the diode elements, drivingthe IGBT elements can be ceased. When a current has flowed into thediode elements, since a gate signal with which the IGBT elements aredriven is not inputted to the IGBT elements, the interference betweenthe action of the diode elements and the action of the IGBT elements canbe avoided.

Since the diode elements and IGBT elements are simultaneously turned on,an increase in the forward voltage of the diode elements attributable tothe fact that the diode elements formed in the same semiconductorsubstrate as the IGBT elements are cannot readily act in a forwarddirection can be avoided. Thus, an increase in a loss in the forwardvoltage of the diode elements can be prevented.

Alternatively, the diode-built-in insulated-gate bipolar transistor mayfurther include a IGBT current sensing element. The IGBT current sensingelement passes current in proportion to current flowing through theinsulated-gate bipolar transistor. The IGBT current sensing element iscoupled with the sensing resistor so that the current passing throughthe IGBT current sensing element flows through the sensing resistor. Thefeedback unit provides an over current threshold, which defines whetherover current passes through the insulated-gate bipolar transistor. Thefeedback unit compares the voltage between two ends of the sensingresistor with the over current threshold. The feedback unit passes thedriving signal to the gate of the insulated-gate bipolar transistor sothat the insulated-gate bipolar transistor turns on when the voltagebetween two ends of the sensing resistor is equal to or smaller than theover current threshold, and the feedback unit stops passing the drivingsignal to the gate of the insulated-gate bipolar transistor so that theinsulated-gate bipolar transistor turns off when the voltage between twoends of the sensing resistor is larger than the first diode currentthreshold.

As mentioned above, since the IGBT sensing elements that sense a currentflowing into the IGBT elements are included, if an over current flowsinto the IGBT elements, driving the IGBT elements can be ceased.Consequently, the IGBT elements can be protected from being broken.

Alternatively, the semiconductor device may further include: atemperature sensing diode element for outputting a forward voltagecorresponding to temperature generated in the diode-built-ininsulated-gate bipolar transistor. The feedback unit further provides asecond diode current threshold, which is larger than the first diodecurrent threshold. The feedback unit replaces the first diode currentthreshold with the second diode current threshold so that the feedbackunit compares the voltage between two ends of the sensing resistor withthe second diode current threshold when the forward voltage is largerthan a predetermined forward voltage. The predetermined forward voltagecorresponds to the temperature in the diode-built-in insulated-gatebipolar transistor equal to or higher than the predeterminedtemperature. The feedback unit passes the driving signal to the gate ofthe insulated-gate bipolar transistor when the voltage between two endsof the sensing resistor is equal to or larger than the second diodecurrent threshold in a case where the forward voltage is larger than thepredetermined forward voltage, and the feedback unit stops passing thedriving signal to the gate of the insulated-gate bipolar transistor whenthe voltage between two ends of the sensing resistor is smaller than thesecond diode current threshold in a case where the forward voltage islarger than the predetermined forward voltage.

Consequently, when the IGBT with a body diode enters thehigh-temperature state, however microscopic a current flowing into thediode elements is, the flow of the current into the diode elements canbe decided. Therefore, when a small current flows into the diodeelements with the IGBT with a body diode left in the high-temperaturestate, driving the IGBT elements can be ceased. Therefore, the IGBT witha body diode can be protected from being broken with the hightemperature.

According to a fourth aspect of the present disclosure, a semiconductordevice includes: a semiconductor substrate; a diode-built-ininsulated-gate bipolar transistor having an insulated-gate bipolartransistor and a diode unit, which are disposed in the substrate,wherein the insulated-gate bipolar transistor includes a gate, and isdriven with a driving signal input into the gate, wherein the diode unitincludes a diode element and a diode current sensing element, andwherein the diode current sensing element passes current in proportionto current flowing through the diode element; a sensing resistor coupledwith the diode current sensing element; and first and second feedbackunits. The first feedback unit provides a decision threshold, whichdefines whether the insulated-gate bipolar transistor is in an on-state.The first feedback unit compares a gate voltage of the insulated-gatebipolar transistor with the decision threshold. The first feedback unitoutputs a first diode current threshold when the gate voltage is largerthan the decision threshold. The first diode current threshold showsthat the insulated-gate bipolar transistor is in the on-state. The firstfeedback unit outputs a second diode current threshold when the gatevoltage is equal to or smaller than the decision threshold. The seconddiode current threshold shows that the insulated-gate bipolar transistoris in an off-state, and the second diode current threshold is largerthan the first diode current threshold. The driving signal is input froman external unit into the second feedback unit. The second feedback unitcompares a voltage between two ends of the sensing resistor with thefirst diode current threshold when the voltage between two ends of thesensing resistor decreases. The feedback unit passes the driving signalto the gate of the insulated-gate bipolar transistor so that theinsulated-gate bipolar transistor turns on when the voltage between twoends of the sensing resistor is equal to or larger than the first diodecurrent threshold in a case where the voltage between two ends of thesensing resistor decreases. The feedback unit stops passing the drivingsignal to the gate of the insulated-gate bipolar transistor so that theinsulated-gate bipolar transistor turns off when the voltage between twoends of the sensing resistor is smaller than the first diode currentthreshold in a case where the voltage between two ends of the sensingresistor decreases. The second feedback unit compares the voltagebetween two ends of the sensing resistor with the second diode currentthreshold when the voltage between two ends of the sensing resistorincreases. The feedback unit stops passing the driving signal to thegate of the insulated-gate bipolar transistor so that the insulated-gatebipolar transistor turns off when the voltage between two ends of thesensing resistor is smaller than the second diode current threshold in acase where the voltage between two ends of the sensing resistorincreases, and the feedback unit passes the driving signal to the gateof the insulated-gate bipolar transistor so that the insulated-gatebipolar transistor turns on when the voltage between two ends of thesensing resistor is equal to or larger than the second diode currentthreshold in a case where the voltage between two ends of the sensingresistor increases.

Consequently, driving the IGBT elements according to the gate potentialof the IGBT elements can be provided with a hysteresis. Specifically,when the IGBT elements are off, a current readily flows into the diodeelements. Therefore, if the potential difference is compared with thesecond diode current sensing threshold smaller than the first diodecurrent sensing threshold, the IGBT elements can be turned off at thetiming at which a current flows into the diode elements. Moreover, whenthe IGBT elements are on, a current cannot readily flow into the diodeelements. Therefore, if the potential difference is compared with thefirst diode current sensing threshold, as long as no current flows intothe diode elements, the IGBT elements can be turned on. Consequently,the IGBT elements can be controlled stably without being vibrated.Moreover, the interference between the action of the diode elements andthe action of the IGBT elements can be avoided in order to prevent anincrease in a forward loss in the diode part.

Alternatively, the diode-built-in insulated-gate bipolar transistor mayfurther include a IGBT current sensing element. The IGBT current sensingelement passes current in proportion to the current of theinsulated-gate bipolar transistor. The IGBT current sensing element iscoupled with the sensing resistor so that the current passing throughthe IGBT current sensing element flows through the sensing resistor. Thesecond feedback unit provides an over current threshold, which defineswhether over current passes through the insulated-gate bipolartransistor. The second feedback unit compares the voltage between twoends of the sensing resistor with the over current threshold. The secondfeedback unit passes the driving signal to the gate of theinsulated-gate bipolar transistor so that the insulated-gate bipolartransistor turns on when the voltage between two ends of the sensingresistor is equal to or smaller than the over current threshold, and thefeedback unit stops passing the driving signal to the gate of theinsulated-gate bipolar transistor so that the insulated-gate bipolartransistor turns off when the voltage between two ends of the sensingresistor is larger than the first diode current threshold.

Consequently, when an overcurrent has flowed into the IGBT elements,driving the IGBT elements can be ceased, and the IGBT elements can beprotected from being broken.

According to a fifth aspect of the present disclosure, a semiconductordevice includes: a semiconductor substrate; a diode-built-ininsulated-gate bipolar transistor having an insulated-gate bipolartransistor unit and a diode unit, which are disposed in the substrate,wherein the insulated-gate bipolar transistor unit includes aninsulated-gate bipolar transistor and an IGBT current sensing element,wherein the insulated-gate bipolar transistor includes a gate, and isdriven with a driving signal input into the gate, wherein the IGBTcurrent sensing element passes current in proportion to current flowingthrough the insulated-gate bipolar transistor, wherein the diode unitincludes a diode element and a diode current sensing element, andwherein the diode current sensing element passes current in proportionto current flowing through the diode element; a sensing resistor coupledwith the IGBT current sensing element and the diode current sensingelement; an IGBT feedback unit; and a diode Schmitt unit. The drivingsignal is input from an external unit into the IGBT feedback unit. TheIGBT feedback unit provides an over current threshold, which defineswhether over current passes through the insulated-gate bipolartransistor. The IGBT feedback unit compares a voltage between two endsof the sensing resistor with the over current threshold. The IGBTfeedback unit passes the driving signal to the gate of theinsulated-gate bipolar transistor so that the insulated-gate bipolartransistor turns on when the voltage between two ends of the sensingresistor is equal to or smaller than the over current threshold. TheIGBT feedback unit stops passing the driving signal to the gate of theinsulated-gate bipolar transistor so that the insulated-gate bipolartransistor turns off when the voltage between two ends of the sensingresistor is larger than the first diode current threshold. The drivingsignal is further input from the external unit into the diode Schmittunit. The diode Schmitt unit provides a first diode current threshold,which defines whether the diode element passes current, and a seconddiode current threshold, which is larger than the first diode currentthreshold. The diode Schmitt unit compares the voltage between two endsof the sensing resistor with the first diode current threshold when thevoltage between two ends of the sensing resistor decreases. The diodeSchmitt unit passes the driving signal to the gate of the insulated-gatebipolar transistor so that the insulated-gate bipolar transistor turnson when the voltage between two ends of the sensing resistor is equal toor larger than the first diode current threshold in a case where thevoltage between two ends of the sensing resistor decreases. The diodeSchmitt unit stops passing the driving signal to the gate of theinsulated-gate bipolar transistor so that the insulated-gate bipolartransistor turns off when the voltage between two ends of the sensingresistor is smaller than the first diode current threshold in a casewhere the voltage between two ends of the sensing resistor decreases.The diode Schmitt unit compares the voltage between two ends of thesensing resistor with the second diode current threshold when thevoltage between two ends of the sensing resistor increases. The diodeSchmitt unit stops passing the driving signal to the gate of theinsulated-gate bipolar transistor so that the insulated-gate bipolartransistor turns off when the voltage between two ends of the sensingresistor is smaller than the second diode current threshold in a casewhere the voltage between two ends of the sensing resistor increases,and the diode Schmitt unit passes the driving signal to the gate of theinsulated-gate bipolar transistor so that the insulated-gate bipolartransistor turns on when the voltage between two ends of the sensingresistor is equal to or larger than the second diode current thresholdin a case where the voltage between two ends of the sensing resistorincreases.

When a current has flowed into the diode elements, driving the IGBTelements can be ceased. The interference between the action of the diodeelements and the action of the IGBT elements can be avoided in order toprevent an increase in a forward loss in the diode part. In this case,since the diode current sensing thresholds have a difference equivalentto a hysteresis, the diode Schmitt means can prevent a chattering fromoccurring during implementation of feedback control in the IGBTelements. Moreover, when an overcurrent has flowed into the IGBTelements, the IGBT feedback means ceases driving the IGBT elements so asto protect the IGBT elements from being broken.

According to a sixth aspect of the present disclosure, a semiconductordevice includes: a semiconductor substrate; a diode-built-ininsulated-gate bipolar transistor having an insulated-gate bipolartransistor unit and a diode unit, which are disposed in the substrate,wherein the insulated-gate bipolar transistor unit includes aninsulated-gate bipolar transistor and an IGBT current sensing element,wherein the insulated-gate bipolar transistor includes a gate, and isdriven with a driving signal input into the gate, wherein the IGBTcurrent sensing element passes current in proportion to current flowingthrough the insulated-gate bipolar transistor, wherein the diode unitincludes a diode element and a diode current sensing element, andwherein the diode current sensing element passes current in proportionto current flowing through the diode element; a first sensing resistorcoupled with the IGBT current sensing element; a second sensing resistorcoupled with the diode current sensing element; an IGBT Schmitt unit;and a diode Schmitt unit. The driving signal is input from an externalunit into the IGBT Schmitt unit.

The IGBT Schmitt unit provides a first over current threshold, whichdefines whether over current passes through the insulated-gate bipolartransistor, and a second over current threshold, which is smaller thanthe first over current threshold. The IGBT Schmitt unit compares a firstvoltage between two ends of the first sensing resistor with the firstover current threshold when the first voltage increases. The IGBTSchmitt unit passes the driving signal to the gate of the insulated-gatebipolar transistor so that the insulated-gate bipolar transistor turnson when the first voltage is equal to or smaller than the first overcurrent threshold in a case where the first voltage increases. The IGBTSchmitt unit stops passing the driving signal to the gate of theinsulated-gate bipolar transistor so that the insulated-gate bipolartransistor turns off when the first voltage is larger than the firstover current threshold in a case where the first voltage increases. TheIGBT Schmitt unit compares the first voltage with the second overcurrent threshold when the first voltage decreases. The IGBT Schmittunit stops passing the driving signal to the gate of the insulated-gatebipolar transistor so that the insulated-gate bipolar transistor turnsoff when the first voltage is larger than the second over currentthreshold in a case where the first voltage decreases. The IGBT Schmittunit passes the driving signal to the gate of the insulated-gate bipolartransistor so that the insulated-gate bipolar transistor turns on whenthe first voltage is equal to or smaller than the second over currentthreshold in a case where the first voltage decreases. The drivingsignal is further input from the external unit into the diode Schmittunit. The diode Schmitt unit provides a first diode current threshold,which defines whether the diode element passes current, and a seconddiode current threshold, which is larger than the first diode currentthreshold. The diode Schmitt unit compares a second voltage between twoends of the second sensing resistor with the first diode currentthreshold when the second voltage decreases. The diode Schmitt unitpasses the driving signal to the gate of the insulated-gate bipolartransistor so that the insulated-gate bipolar transistor turns on whenthe second voltage is equal to or larger than the first diode currentthreshold in a case where the second voltage decreases. The diodeSchmitt unit stops passing the driving signal to the gate of theinsulated-gate bipolar transistor so that the insulated-gate bipolartransistor turns off when the second voltage is smaller than the firstdiode current threshold in a case where the second voltage decreases.The diode Schmitt unit compares the second voltage with the second diodecurrent threshold when the second voltage increases. The diode Schmittunit stops passing the driving signal to the gate of the insulated-gatebipolar transistor so that the insulated-gate bipolar transistor turnsoff when the second voltage is smaller than the second diode currentthreshold in a case where the second voltage increases, and the diodeSchmitt unit passes the driving signal to the gate of the insulated-gatebipolar transistor so that the insulated-gate bipolar transistor turnson when the second voltage is equal to or larger than the second diodecurrent threshold in a case where the second voltage increases.

Consequently, an increase in a forward loss in the diode part can beprevented, and a chattering by the IGBT elements can be prevented.Moreover, since a current flowing into the IGBT sensing elements and acurrent flowing into the diode elements are sensed by the differentsense resistors, the thresholds can be designed according to the outputcharacteristics of the IGBT sensing elements and diode sensing elements.

According to a seventh aspect of the present disclosure, a semiconductordevice includes: a semiconductor substrate having a first conductivitytype, having a first principal surface and a second principal surface,and including a main region and a sensing region, wherein an area of thesensing region on the first principal surface is smaller than the mainregion; a diode-built-in insulated-gate bipolar transistor having aninsulated-gate bipolar transistor and a free wheel diode, which aredisposed in the main region of the substrate, wherein the insulated-gatebipolar transistor has a gate electrode, and is driven with a drivingsignal input into the gate electrode; and a diode current sensingelement disposed in the sensing region of the substrate. The free wheeldiode includes a FWD anode having a second conductive type and a FWDcathode having the first conductive type. The FWD anode is provided by afirst surface portion of the main region in the substrate on the firstprincipal surface, and provides a base of the insulated-gate bipolartransistor. The FWD cathode is disposed in a second surface portion ofthe main region in the substrate on the second principal surface. Theinsulated-gate bipolar transistor includes a collector disposed in athird surface portion of the main region in the substrate on the secondprincipal surface, which is different from the second surface portion.The diode current sensing element includes a sensing element anodehaving the second conductive type. The sensing element anode is disposedin a fourth surface portion of the sensing region in the substrate onthe first principal surface, and the diode current sensing elementpasses current in proportion to current flowing through the free wheeldiode.

As mentioned above, according to the present invention, the diode-onlysensing elements are formed within the sense region. The diode-onlysensing elements have no gate electrode through which a gate drivingsignal is inputted, and are thus formed to remain unaffected by a gatepotential. Consequently, a current proportional to a current flowinginto the commutation diode elements readily flows into the diode-onlysensing elements (a detective voltage can be readily developed).Therefore, as long as the diode-only sensing elements are employed, afeedback means that controls whether the gate driving signal should beinputted through the gate electrodes can be highly precisely put intoaction according to whether a current has flowed into the commutationdiode elements. In other words, although the commutation diode elementsare incorporated in the IGBT elements, an increase in a forward losscaused by the commutation diode elements can be effectively suppressed.

Alternatively, the semiconductor device may further include: wherein thediode current sensing element further includes a sensing element cathodehaving the first conductive type. The sensing element cathode isdisposed in a fifth surface portion of the sensing region in thesubstrate on the second principal surface, and the sensing elementcathode is spaced apart from the base of the insulated-gate bipolartransistor by a predetermined distance along with a direction parallelto the first principal surface.

Owing to the above construction, at least part of carriers accumulatedin the semiconductor substrate within the main cell region along withthe action of the IGBT elements (holes injected from the collectorregions included in the IGBT elements) flows into the cathode regions ofthe diode-only sensing elements. This prevents the incorrect action ofthe diode-only sensing elements. Namely, current detection to beperformed using the diode-only sensing elements can be more accuratelyachieved according to a current flowing into the commutation diodeelements.

Further, the sensing element anode may be disposed just over the sensingelement cathode.

Owing to the above construction, the action resistance offered by thediode-only sensing elements can be reduced so that a current can morereadily flow (a detective voltage can be readily developed).

Alternatively, the diode current sensing element may further include asensing element cathode having the first conductive type. The FWDcathode provides the sensing element cathode.

Alternatively, the gate electrode may be disposed in a gate trench viaan insulation film. The gate trench is disposed in the first surfaceportion of the main region in the substrate on the first principalsurface, and penetrates the base of the insulated-gate bipolartransistor so that the gate trench reaches the substrate. The diodecurrent sensing element further includes a dummy gate electrode, whichis electrically grounded. The dummy gate electrode is disposed in adummy gate trench via an insulation film, and the dummy gate trench isdisposed in the fourth surface portion of the sensing region in thesubstrate on the first principal surface, and penetrates the sensingelement anode of the diode current sensing element so that the dummygate trench reaches the substrate.

Owing to the above construction, since the dummy gate electrodes aregrounded but are not electrically connected to the gate electrodes ofthe IGBT elements. Although the dummy gate electrodes having the samestructure as the gate electrodes do are included, the action of thediode-only sensing elements will remain unaffected by the gatepotential. Moreover, a design ensuring a dielectric strength may beidentical to that for the commutation diode elements within the mainregion.

Alternatively, the semiconductor device may further include: a IGBTcurrent sensing element disposed in the sensing region of the substrate.The IGBT current sensing element includes a sensing element base havingthe second conductive type, a sensing element gate electrode, a sensingelement emitter having the first conductive type, and a sensing elementcollector having the second conductive type.

The sensing element base is provided by a sixth surface portion of thesensing region in the substrate on the first principal surface. Thesensing element gate electrode is disposed in a sensing element gatetrench via an insulation film. The sensing element gate trench isdisposed in the sixth surface portion of the sensing region in thesubstrate on the first principal surface, and penetrates the sensingelement base of the IGBT current sensing element so that the sensingelement gate trench reaches the substrate. The sensing element emitteris disposed in the sixth surface portion of the sensing region in thesubstrate on the first principal surface, and is adjacent to the sensingelement gate trench. The sensing element collector is disposed in aseventh surface portion of the sensing region in the substrate on thesecond principal surface, and the IGBT current sensing element passescurrent in proportion to current flowing through the insulated-gatebipolar transistor.

Owing to the above structure, by sensing the current flowing into theIGBT-only sensing elements, the IGBT elements can be protected from anover current.

Further, the sensing element cathode of the diode current sensingelement may be spaced apart from the sensing element base of the IGBTcurrent sensing element by a predetermined distance along with thedirection parallel to the first principal surface.

Owing to the above construction, at least part of carriers accumulatedin the semiconductor substrate along with the action of the IGBT-onlysensing elements (holes injected from the collector regions included inthe IGBT-only sensing elements) flows into the cathode regions of thediode-only sensing elements. This prevents the incorrect action of thediode-only sensing elements. In other words, current detection to beperformed using the diode-only sensing elements can be more accuratelyachieved according to the current flowing into the commutation diodeelements.

Alternatively, the semiconductor device may further include: a IGBTcurrent sensing element disposed in the sensing region of the substrate.The IGBT current sensing element includes a sensing element base havingthe second conductive type, a sensing element gate electrode, a sensingelement emitter having the first conductive type, and a sensing elementcollector having the second conductive type.

The sensing element base is provided by a sixth surface portion of thesensing region in the substrate on the first principal surface. Thesensing element gate electrode is disposed in a sensing element gatetrench via an insulation film. The sensing element gate trench isdisposed in a center of the sixth surface portion of the sensing regionin the substrate on the first principal surface, and penetrates thesensing element base of the IGBT current sensing element so that thesensing element gate trench reaches the substrate. The sensing elementemitter is disposed in the sixth surface portion of the sensing regionin the substrate on the first principal surface, and is adjacent to thesensing element gate trench. The sensing element collector is disposedin a seventh surface portion of the sensing region in the substrate onthe second principal surface. The IGBT current sensing element passescurrent in proportion to current flowing through the insulated-gatebipolar transistor. The sensing element base includes a part, which isdisposed on a periphery from the center of the sixth surface portion.The part of the sensing element base provides the sensing element anode,and the sensing element cathode is spaced apart from the sensing elementbase by a predetermined distance along with the direction parallel tothe first principal surface.

While the invention has been described with reference to preferredembodiments thereof, it is to be understood that the invention is notlimited to the preferred embodiments and constructions. The invention isintended to cover various modification and equivalent arrangements. Inaddition, while the various combinations and configurations, which arepreferred, other combinations and configurations, including more, lessor only a single element, are also within the spirit and scope of theinvention.

1-13. (canceled)
 14. A semiconductor device comprising: a semiconductorsubstrate; a diode-built-in insulated-gate bipolar transistor having aninsulated-gate bipolar transistor and a diode unit, which are disposedin the substrate, wherein the insulated-gate bipolar transistor includesa gate, and is driven with a driving signal input into the gate, whereinthe diode unit includes a diode element and a diode current sensingelement, and wherein the diode current sensing element passes current inproportion to current flowing through the diode element; a sensingresistor coupled with the diode current sensing element; and a feedbackunit, wherein the driving signal is input from an external unit into thefeedback unit, wherein the feedback unit provides a first diode currentthreshold, which defines whether the diode element passes current,wherein the feedback unit compares a voltage between two ends of thesensing resistor with the first diode current threshold, wherein thefeedback unit passes the driving signal to the gate of theinsulated-gate bipolar transistor so that the insulated-gate bipolartransistor turns on when the voltage between two ends of the sensingresistor is equal to or larger than the first diode current threshold,and wherein the feedback unit stops passing the driving signal to thegate of the insulated-gate bipolar transistor so that the insulated-gatebipolar transistor turns off when the voltage between two ends of thesensing resistor is smaller than the first diode current threshold. 15.The semiconductor device according to claim 14, wherein thediode-built-in insulated-gate bipolar transistor further includes a IGBTcurrent sensing element, wherein the IGBT current sensing element passescurrent in proportion to current flowing through the insulated-gatebipolar transistor, and wherein the IGBT current sensing element iscoupled with the sensing resistor so that the current passing throughthe IGBT current sensing element flows through the sensing resistor,wherein the feedback unit provides an over current threshold, whichdefines whether over current passes through the insulated-gate bipolartransistor, wherein the feedback unit compares the voltage between twoends of the sensing resistor with the over current threshold, whereinthe feedback unit passes the driving signal to the gate of theinsulated-gate bipolar transistor so that the insulated-gate bipolartransistor turns on when the voltage between two ends of the sensingresistor is equal to or smaller than the over current threshold, andwherein the feedback unit stops passing the driving signal to the gateof the insulated-gate bipolar transistor so that the insulated-gatebipolar transistor turns off when the voltage between two ends of thesensing resistor is larger than the first diode current threshold. 16.The semiconductor device according to claim 14, further comprising: atemperature sensing diode element for outputting a forward voltagecorresponding to temperature generated in the diode-built-ininsulated-gate bipolar transistor, wherein the feedback unit furtherprovides a second diode current threshold, which is larger than thefirst diode current threshold, wherein the feedback unit replaces thefirst diode current threshold with the second diode current threshold sothat the feedback unit compares the voltage between two ends of thesensing resistor with the second diode current threshold when theforward voltage is larger than a predetermined forward voltage, whereinthe predetermined forward voltage corresponds to the temperature in thediode-built-in insulated-gate bipolar transistor equal to or higher thanthe predetermined temperature, wherein the feedback unit passes thedriving signal to the gate of the insulated-gate bipolar transistor whenthe voltage between two ends of the sensing resistor is equal to orlarger than the second diode current threshold in a case where theforward voltage is larger than the predetermined forward voltage, andwherein the feedback unit stops passing the driving signal to the gateof the insulated-gate bipolar transistor when the voltage between twoends of the sensing resistor is smaller than the second diode currentthreshold in a case where the forward voltage is larger than thepredetermined forward voltage.
 17. A semiconductor device comprising: asemiconductor substrate; a diode-built-in insulated-gate bipolartransistor having an insulated-gate bipolar transistor and a diode unit,which are disposed in the substrate, wherein the insulated-gate bipolartransistor includes a gate, and is driven with a driving signal inputinto the gate, wherein the diode unit includes a diode element and adiode current sensing element, and wherein the diode current sensingelement passes current in proportion to current flowing through thediode element; a sensing resistor coupled with the diode current sensingelement; and first and second feedback units, wherein the first feedbackunit provides a decision threshold, which defines whether theinsulated-gate bipolar transistor is in an on-state, wherein the firstfeedback unit compares a gate voltage of the insulated-gate bipolartransistor with the decision threshold, wherein the first feedback unitoutputs a first diode current threshold when the gate voltage is largerthan the decision threshold, wherein the first diode current thresholdshows that the insulated-gate bipolar transistor is in the on-state,wherein the first feedback unit outputs a second diode current thresholdwhen the gate voltage is equal to or smaller than the decisionthreshold, wherein the second diode current threshold shows that theinsulated-gate bipolar transistor is in an off-state, and the seconddiode current threshold is larger than the first diode currentthreshold, wherein the driving signal is input from an external unitinto the second feedback unit, wherein the second feedback unit comparesa voltage between two ends of the sensing resistor with the first diodecurrent threshold when the voltage between two ends of the sensingresistor decreases, wherein the second feedback unit passes the drivingsignal to the gate of the insulated-gate bipolar transistor so that theinsulated-gate bipolar transistor turns on when the voltage between twoends of the sensing resistor is equal to or larger than the first diodecurrent threshold in a case where the voltage between two ends of thesensing resistor decreases, wherein the second feedback unit stopspassing the driving signal to the gate of the insulated-gate bipolartransistor so that the insulated-gate bipolar transistor turns off whenthe voltage between two ends of the sensing resistor is smaller than thefirst diode current threshold in a case where the voltage between twoends of the sensing resistor decreases, wherein the second feedback unitcompares the voltage between two ends of the sensing resistor with thesecond diode current threshold when the voltage between two ends of thesensing resistor increases, wherein the second feedback unit stopspassing the driving signal to the gate of the insulated-gate bipolartransistor so that the insulated-gate bipolar transistor turns off whenthe voltage between two ends of the sensing resistor is smaller than thesecond diode current threshold in a case where the voltage between twoends of the sensing resistor increases, and wherein the second feedbackunit passes the driving signal to the gate of the insulated-gate bipolartransistor so that the insulated-gate bipolar transistor turns on whenthe voltage between two ends of the sensing resistor is equal to orlarger than the second diode current threshold in a case where thevoltage between two ends of the sensing resistor increases.
 18. Thesemiconductor device according to claim 17, wherein the diode-built-ininsulated-gate bipolar transistor further includes a IGBT currentsensing element, wherein the IGBT current sensing element passes currentin proportion to the current of the insulated-gate bipolar transistor,wherein the IGBT current sensing element is coupled with the sensingresistor so that the current passing through the IGBT current sensingelement flows through the sensing resistor, wherein the second feedbackunit provides an over current threshold, which defines whether overcurrent passes through the insulated-gate bipolar transistor, whereinthe second feedback unit compares the voltage between two ends of thesensing resistor with the over current threshold, wherein the secondfeedback unit passes the driving signal to the gate of theinsulated-gate bipolar transistor so that the insulated-gate bipolartransistor turns on when the voltage between two ends of the sensingresistor is equal to or smaller than the over current threshold, andwherein the second feedback unit stops passing the driving signal to thegate of the insulated-gate bipolar transistor so that the insulated-gatebipolar transistor turns off when the voltage between two ends of thesensing resistor is larger than the first diode current threshold.
 19. Asemiconductor device comprising: a semiconductor substrate; adiode-built-in insulated-gate bipolar transistor having aninsulated-gate bipolar transistor unit and a diode unit, which aredisposed in the substrate, wherein the insulated-gate bipolar transistorunit includes an insulated-gate bipolar transistor and an IGBT currentsensing element, wherein the insulated-gate bipolar transistor includesa gate, and is driven with a driving signal input into the gate, whereinthe IGBT current sensing element passes current in proportion to currentflowing through the insulated-gate bipolar transistor, wherein the diodeunit includes a diode element and a diode current sensing element, andwherein the diode current sensing element passes current in proportionto current flowing through the diode element; a sensing resistor coupledwith the IGBT current sensing element and the diode current sensingelement; an IGBT feedback unit; and a diode Schmitt unit, wherein thedriving signal is input from an external unit into the IGBT feedbackunit, wherein the IGBT feedback unit provides an over current threshold,which defines whether over current passes through the insulated-gatebipolar transistor, wherein the IGBT feedback unit compares a voltagebetween two ends of the sensing resistor with the over currentthreshold, wherein the IGBT feedback unit passes the driving signal tothe gate of the insulated-gate bipolar transistor so that theinsulated-gate bipolar transistor turns on when the voltage between twoends of the sensing resistor is equal to or smaller than the overcurrent threshold, wherein the IGBT feedback unit stops passing thedriving signal to the gate of the insulated-gate bipolar transistor sothat the insulated-gate bipolar transistor turns off when the voltagebetween two ends of the sensing resistor is larger than the first diodecurrent threshold, wherein the driving signal is further input from theexternal unit into the diode Schmitt unit, wherein the diode Schmittunit provides a first diode current threshold, which defines whether thediode element passes current, and a second diode current threshold,which is larger than the first diode current threshold, wherein thediode Schmitt unit compares the voltage between two ends of the sensingresistor with the first diode current threshold when the voltage betweentwo ends of the sensing resistor decreases, wherein the diode Schmittunit passes the driving signal to the gate of the insulated-gate bipolartransistor so that the insulated-gate bipolar transistor turns on whenthe voltage between two ends of the sensing resistor is equal to orlarger than the first diode current threshold in a case where thevoltage between two ends of the sensing resistor decreases, wherein thediode Schmitt unit stops passing the driving signal to the gate of theinsulated-gate bipolar transistor so that the insulated-gate bipolartransistor turns off when the voltage between two ends of the sensingresistor is smaller than the first diode current threshold in a casewhere the voltage between two ends of the sensing resistor decreases,wherein the diode Schmitt unit compares the voltage between two ends ofthe sensing resistor with the second diode current threshold when thevoltage between two ends of the sensing resistor increases, wherein thediode Schmitt unit stops passing the driving signal to the gate of theinsulated-gate bipolar transistor so that the insulated-gate bipolartransistor turns off when the voltage between two ends of the sensingresistor is smaller than the second diode current threshold in a casewhere the voltage between two ends of the sensing resistor increases,and wherein the diode Schmitt unit passes the driving signal to the gateof the insulated-gate bipolar transistor so that the insulated-gatebipolar transistor turns on when the voltage between two ends of thesensing resistor is equal to or larger than the second diode currentthreshold in a case where the voltage between two ends of the sensingresistor increases.
 20. A semiconductor device comprising: asemiconductor substrate; a diode-built-in insulated-gate bipolartransistor having an insulated-gate bipolar transistor unit and a diodeunit, which are disposed in the substrate, wherein the insulated-gatebipolar transistor unit includes an insulated-gate bipolar transistorand an IGBT current sensing element, wherein the insulated-gate bipolartransistor includes a gate, and is driven with a driving signal inputinto the gate, wherein the IGBT current sensing element passes currentin proportion to current flowing through the insulated-gate bipolartransistor, wherein the diode unit includes a diode element and a diodecurrent sensing element, and wherein the diode current sensing elementpasses current in proportion to current flowing through the diodeelement; a first sensing resistor coupled with the IGBT current sensingelement; a second sensing resistor coupled with the diode currentsensing element; an IGBT Schmitt unit; and a diode Schmitt unit, whereinthe driving signal is input from an external unit into the IGBT Schmittunit, wherein the IGBT Schmitt unit provides a first over currentthreshold, which defines whether over current passes through theinsulated-gate bipolar transistor, and a second over current threshold,which is smaller than the first over current threshold, wherein the IGBTSchmitt unit compares a first voltage between two ends of the firstsensing resistor with the first over current threshold when the firstvoltage increases, wherein the IGBT Schmitt unit passes the drivingsignal to the gate of the insulated-gate bipolar transistor so that theinsulated-gate bipolar transistor turns on when the first voltage isequal to or smaller than the first over current threshold in a casewhere the first voltage increases, wherein the IGBT Schmitt unit stopspassing the driving signal to the gate of the insulated-gate bipolartransistor so that the insulated-gate bipolar transistor turns off whenthe first voltage is larger than the first over current threshold in acase where the first voltage increases, wherein the IGBT Schmitt unitcompares the first voltage with the second over current threshold whenthe first voltage decreases, wherein the IGBT Schmitt unit stops passingthe driving signal to the gate of the insulated-gate bipolar transistorso that the insulated-gate bipolar transistor turns off when the firstvoltage is larger than the second over current threshold in a case wherethe first voltage decreases, wherein the IGBT Schmitt unit passes thedriving signal to the gate of the insulated-gate bipolar transistor sothat the insulated-gate bipolar transistor turns on when the firstvoltage is equal to or smaller than the second over current threshold ina case where the first voltage decreases, wherein the driving signal isfurther input from the external unit into the diode Schmitt unit,wherein the diode Schmitt unit provides a first diode current threshold,which defines whether the diode element passes current, and a seconddiode current threshold, which is larger than the first diode currentthreshold, wherein the diode Schmitt unit compares a second voltagebetween two ends of the second sensing resistor with the first diodecurrent threshold when the second voltage decreases, wherein the diodeSchmitt unit passes the driving signal to the gate of the insulated-gatebipolar transistor so that the insulated-gate bipolar transistor turnson when the second voltage is equal to or larger than the first diodecurrent threshold in a case where the second voltage decreases, whereinthe diode Schmitt unit stops passing the driving signal to the gate ofthe insulated-gate bipolar transistor so that the insulated-gate bipolartransistor turns off when the second voltage is smaller than the firstdiode current threshold in a case where the second voltage decreases,wherein the diode Schmitt unit compares the second voltage with thesecond diode current threshold when the second voltage increases,wherein the diode Schmitt unit stops passing the driving signal to thegate of the insulated-gate bipolar transistor so that the insulated-gatebipolar transistor turns off when the second voltage is smaller than thesecond diode current threshold in a case where the second voltageincreases, and wherein the diode Schmitt unit passes the driving signalto the gate of the insulated-gate bipolar transistor so that theinsulated-gate bipolar transistor turns on when the second voltage isequal to or larger than the second diode current threshold in a casewhere the second voltage increases. 21-28. (canceled)